Laminated film

ABSTRACT

A width-direction multilayer laminated film having a large area and uniform optical properties is provided. A light guide, a light diffusion film, a light collecting film, a viewing angle control film, and an optical waveguide film, which are low cost and have excellent optical properties, as well as an illuminating device, a communication device, and a display using these films. The laminated film may include at least a structure in which a layer made of resin A (layer A) and a layer made of resin B (layer B) are alternately laminated in the width direction, wherein the width of the film is 400 mm or more and the number of layer Bs, each having a cross-sectional width from 0.1 μm to 10,000 μm, is 10 or larger.

This application is a U.S. National Phase Application of PCTInternational Application No. PCT/JP2009/053908, filed Mar. 3, 2009,which claims priority to Japanese Patent Application No. 2008-065317,filed Mar. 14, 2008, the contents of each of these applications beingincorporated by reference herein in their entirety.

TECHNICAL FIELD

The present invention relates to a laminated film and a film rollthereof. The present invention also relates to a film suitable for alight guide, a light diffusion film, a light-collecting film, a viewingangle control film, an optical waveguide film and the like, and to anilluminating device, a communication device, a display and the likeusing the same.

BACKGROUND OF THE INVENTION

A backlight display has become widespread in which a liquid crystallayer is illuminated from the backside to emit light. On the undersideof the liquid crystal layer, a backlight unit is provided. The backlightunit is generally equipped with a bar-shaped lamp as a light source anda plurality of laminated optical sheets. Each of these optical sheetshas specific optical characteristics such as refraction and diffusion.Specific examples of the optical sheet include: a square plate-shapedlight guide plate whose end portion is arranged along a lamp; a lightdiffusion sheet provided on the surface of the light guide plate; alight-collecting sheet such as a prism sheet which is arranged on thesurface of the diffusion sheet. Another type of the backlight unit is,for example, of a direct backlight type in which a lamp is located onthe non-display side of a display and optical sheets are located betweenthe lamp and the display.

A sheet (Patent Literature 1) has been recently proposed which has bothfunctions of a diffusion sheet and a function of a light-collectingsheet, that is, has an enhanced changing a direction function of lightwithout decreasing the amount of light emission in the normal direction.When such a sheet is employed, there are effects that the brightness ofthe display is increased and that the display is made thinner byreducing the number of the optical sheets in a backlight unit and byreducing the distance between the lamp and the display.

Such a sheet is proposed to be manufactured by a method in which twokinds of synthetic resins are multilayered in the width direction by amixer. It is, however, not possible to obtain a sheet which has a largearea and a uniform performance by this method. This is becausedisappearance of a layer, unification of layers or the like is caused bya considerable flow disturbance due to repeated deformations by a mixeror a deformation through an extrusion die when a very large number oflayers each having a minute width are to be obtained by the mixermethod.

Such a method of laminating sheets in the width direction by using amixer is also disclosed, for example, in Patent Literature 2. Even incases where the number of layers is small, deformation of the layers isinevitable, as shown in FIG. 1 and FIG. 2 of Patent Literature 2.

In addition, a method is proposed in which an optical interconnection isobtained by using a complex device having a large number of slits(Patent Literature 3). In this method, a width-direction multilayerlaminated film with a higher precision compared with a film obtained bya method in which a mixer is employed, can be obtained; however, theupper limit of the substantial number of the layers aligned in a line is301, the shape, position and cross section area of the core layer ishard to be stable due to the configuration of the die and therefore, andit was difficult to obtain a width direction multilayer laminated filmhaving a large area.

Patent Literature 1: JP 2001-91708 A

Patent Literature 2: JP 51-33177 A

Patent Literature 3: JP 2006-221145 A

SUMMARY OF THE INVENTION

In view of the above-described problems associated with conventionaltechniques, the present invention provides a width-direction multilayerlaminated film having a large area and uniform optical properties. Thepresent invention also provides a light guide, a light diffusion film, alight-collecting film, a viewing angle control film, and an opticalwaveguide film, which are low cost and have excellent opticalproperties, and an illuminating device, a communication device and adisplay using these films.

The laminated film preferably has at least a structure in which a layermade of resin A (layer A) and a layer made of resin B (layer B) arealternately laminated in the width direction, wherein the width of thefilm is 400 mm or more and the number of layer Bs each having across-sectional width of 0.1 μm or more and 10,000 μm or less is 10 ormore.

The laminated film of the present invention can be a width-directionmultilayer laminated film having a large area and uniform opticalproperties. Since a width-direction multilayer laminated film having alarge area can be obtained, the film can be manufactured at very lowcost. Further, in an embodiment of a film whose part of end portion isbranched, it is easy to connect the film to an illuminating device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating an example of the laminatedfilm of the present invention.

FIG. 2 is a perspective view illustrating an example of the laminatedfilm of the present invention.

FIG. 3 illustrates plan views showing an example of the extrusion die ofthe present invention.

FIG. 4 is a perspective view of a nozzle section 6.

FIG. 5 is a cross-sectional view illustrating the internal structure ofan example of the extrusion die of the present invention.

FIG. 6 illustrates plan views showing an example of the extrusion die ofanother embodiment of the present invention different from thatillustrated in FIG. 3.

FIG. 7 is a cross-sectional view illustrating the internal structure ofan example of the extrusion die according to another embodiment of thepresent invention different from that illustrated in FIG. 5.

FIG. 8 is a cross-sectional view illustrating the internal structure ofan example of the extrusion die of the present invention, taken alongthe line X-X in FIG. 7.

FIG. 9 is a cross-sectional view illustrating the internal structure ofan example of an extrusion die according to another embodiment of thepresent invention.

FIG. 10 is a cross-sectional view illustrating the internal structure ofan example of an extrusion die according to another embodiment of thepresent invention.

FIG. 11 is a cross-sectional view illustrating the internal structure ofan example of the extrusion die, taken along the line A-A in FIGS. 9 and10.

FIG. 12 is a plan view of a multi-hole plate 26 as viewed from theupstream side.

DESCRIPTION OF SYMBOLS

-   1: resin A-   2: resin B-   3: resin (polymer) inlet section-   4: manifold section-   5: first slit section-   6: nozzle section-   7: second manifold section-   8: junction-   9: second slit section-   10: extrusion die-   11: nozzle-   12: junction-   13: extrusion die-   14: hole-   21: extrusion die-   22: guide port-   23: guide port-   24: flow path-   25: manifold-   26: multi-hole plate-   27: hole-   28: flow path-   29: manifold-   30: junction-   31: lip

DETAILED DESCRIPTION OF THE INVENTION

It is preferred that a laminated film of the present invention have atleast a structure in which the layer made of resin A (layer A) and thelayer made of resin B (layer B) are alternately laminated in the widthdirection, wherein the width of the film is 400 mm or more and thenumber of layer Bs each having a cross-sectional area of 0.1 μm or moreand 10,000 μm or less is 10 or larger. Such a laminated film has a largearea and can attain uniform optical properties.

In the following description, the shape of layers A and B are describedby using a cross-section taken along the film width direction and thefilm thickness direction, unless otherwise specifically noted.

Although the resin used for the laminated film of the present inventionis not restricted, one which comprises a thermoplastic resin isparticularly preferred. By using the resin which comprises athermoplastic resin, laminated films can be easily obtained byco-extrusion molding method and, in addition, surface processing such asthermal imprint process can be easily applied to the laminated filmsobtained, thereby allowing for producing the desired laminated films ata low cost. Examples of the thermoplastic resin which can be usedinclude polyolefin resins such as polyethylene, polypropylene,polystyrene, and polymethylpentene; alicyclic polyolefin resins;polyamide resins such as nylon 6 and nylon 66; aramid resins; polyesterresins such as polyethylene terephthalate, polybutylene terephthalate,polypropylene terephthalate, polybutyl succinate andpolyethylene-2,6-naphthalate; polycarbonate resins; polyarylate resins;polyacetal resins; polyphenylene sulfide resins; fluorocarbon resinssuch as tetrafluoroethylene resins, trifluoroethylene resins,chlorotrifluoroethylene resins, tetrafluoroethylene-hexafluoropropylenecopolymer and vinylidene fluoride resins; acrylic resins such as PMMA;polyacetal resins; polyglycolic acid resins; and polylactic acid resins.

The resin may be one which comprises only one type of repeating unit,copolymer or a mixture of two or more resins. Further, to the resin,various additives such as an antioxidant, antistatic agent, nucleusagent, inorganic particles, organic particles, viscosity-reducing agent,thermal stabilizer, lubricant, infrared absorber, UV absorber and adoping agent for adjusting refractive index may be added.

In particular, since the laminated film preferably exhibits a highstrength, heat resistance and transparency and to prevent propagationloss when the light is guided through the sheet, the film is preferredto be polycarbonate; polymethylmethacrylate; cyclic olefin copolymerwhich is a copolymer between norbornene and ethylene copolymerized bymetallocene or a Ziegler-Natta catalyst; cyclic polyolefin obtained byring-opening metathesis polymerization and hydrogenation of anorbornene-based monomer; polyimide resin; poly (4-methylpentene-1);polyethylene terephthalate; polystyrene; or fluorinated polymer.Further, to reduce the propagation loss, it is more preferable that thehydrogen atoms in the polymer be deuterated.

In the resin used for the laminated film of the present invention, resinA and/or resin B preferably contain particles having light diffusibilitysuch as inorganic particles and organic particles. In this case wherethe resin A and/or resin B contain the particles having lightdiffusibility such as inorganic particles and organic particles, it ispossible to impart a higher light diffusibility due to light scatteringby the contained particles. Examples of such particles include alumina,aluminum hydroxide, magnesium hydroxide, talc, glass bead, sodiumsilicate, calcium carbonate, barium carbonate, titanium oxide, andsilica. It is also preferred that, as resin A and/or resin B, one inwhich a resin different from the resin that is a major constituent ofthe resin A and/or B is dispersed be used. In particular, by dispersingthe resin whose refractive index is different from that of the dispersedresin, light can be scattered using the light refraction and reflectionwhich occur at the interface between resins, thereby allowing forimpartation of high light diffusibility. In the present invention, suchdispersed resin is also considered to be within the concept and meaningof a particle because it has the same effect as that of the particlesdescribed above.

In the laminated film of the present invention, it is preferable thatparticles are contained only in the layer B, and it is also preferablethat particles are contained in both the layers A and B and an areafraction of the particles contained in the layer B (which refers to aratio of the particle portion to the layer in a cross-sectional image)is larger than that of the particles contained in the layer A. In thiscase, diffusion of the light transmitting through the layer made ofresin A (layer A) is larger than diffusion of the light transmittingthrough the layer made of resin B (layer B). Because of this differencein the light diffusibility, for example, in cases where the laminatedfilm is used for suppressing ununiformity of the backlight brightness,by arranging the layer B above the lamps and the layer A between thelamps, the ununiformity in the brightness originating from the lamps canbe suppressed effectively.

In the laminated film of this invention, it is also preferable that boththe layers A and B contain particles and the particle diameter of theparticles contained in the layer B is smaller than that of the particlescontained in the layer A. The particle diameter as used herein indicatesa particle diameter of an inorganic or organic particle, and adispersion diameter of resin. If there is a variation in particlediameters and dispersion diameters, an average value is used. Also inthis case, diffusion of the light transmitting through the layer made ofresin A (layer A) is larger than diffusion of the light transmittingthrough the layer made of resin B (layer B). Because of this differencein the light diffusibility, for example, in cases where the laminatedfilm is used for suppressing ununiformity of the backlight brightness,by arranging the layer B above the lamps and the layer A between thelamps, the ununiformity in the brightness originating from the lamps canbe suppressed effectively.

The laminated film of the present invention preferably has at least thestructure in which the layer made of resin A (layer A) and the layermade of resin B (layer B) are alternately laminated in the widthdirection. The resin A and resin B are different resins or preferablyhave different types and amounts of contained additives. Further, asillustrated in FIGS. 1 and 2, the structure in which the layers arealternately laminated in the width direction is a structure in which atleast the layers A and B are alternately arranged in the width directionin a partial region in the film as viewed in a film thicknessdirection-film width direction cross-sectional view. FIGS. 1 and 2illustrate perspective views of examples of the laminated film accordingto embodiments of the present invention. It is not necessarily requiredthat the width direction length (lengths) and the thickness directionlength (lengths) of the layer A and/or layer B be the same. It ispreferable that the layer A and/or layer B are substantially continuousin the vertical direction (longitudinal direction). In this case, sincea film not changing the optical characteristics in the verticaldirection can be obtained, ununiformity of the optical characteristicsof a display mounted with the film can be suppressed. Since a sheetwithout ununiformity of the optical characteristics can be obtainedsimply by cutting a continuously manufactured film at a desired length,it also becomes possible to manufacture an optical sheet at a low cost.

The laminated film of the present invention is optionally characterizedin that optical diffusion and optical collection can be given by usingrefraction and reflection at the interface between the alternatelylaminated layers A and B. Therefore, in the laminated film of thepresent invention, it is preferable that the refractive indexdifference, |nb−na|, is 0.001 or larger, where na is the refractiveindex of the resin A and nb is the refractive index of the resin B. Therefractive indices of the resins A and B are the refractive indices ofthe resin constituting the layer A and B, respectively. If the layercontains a mixture of a plurality of resins and additives, it is assumedthat the refractive index of the mixture is the refractive index of theresins A and resins B. With the refractive index difference between theresins A and B being 0.001 or larger, optical refraction and reflectionoccur at the interface, so that optical diffusion and collection can beexhibited. The degree of the difference in the refractive indices of theresins A and B can be set arbitrarily in accordance with the laminatedstructure of the layers A and B, and desired optical diffusion andcollection. The refractive index difference is more preferably 0.010 orlarger, still more preferably 0.030 or larger, and most preferably 0.06or larger. As the refractive index difference becomes large, a rangeapplied to optical sheet design can be broadened such as a largerincidence angle for total reflection at an interface and largerrefractive indices, and a variety of optical characteristics that may begiven to the laminated film can be increased. A combination ofpreferable resins A and B providing a refractive index difference|nb−na| of 0.001 or larger may be selected arbitrary, for example, fromthe above-described resins.

The laminated film preferably has a film width of 400 mm or wider, andthe number of layer Bs each preferably having a cross-sectional widthfrom 0.1 μm to 10,000 μm be 10 or more. The cross-sectional width asused herein refers to the maximum length of each of the layer Bs in thewidth direction in the thickness direction-width direction cross-sectionof the laminated film. If the cross-sectional width of the layer B isnarrower than 0.1 μm, the cross-sectional width of an optical sheet usedfor a display becomes smaller than the wavelength of light used fordisplaying, so that the refraction and reflection at the interface donot occur and target optical characteristics may not be obtained.Further, if the cross-sectional width of the layer B is wider than10,000 μm, the layer B has a shape of an extremely flat plane and if thelaminated film is mounted in a display, it becomes difficult to obtain auniform brightness distribution on the screen. The lower limit of thelayer B cross-sectional width is preferably 10 μm or larger, and theupper limit of the layer B cross-sectional width is preferably 1,600 μmor less. If the laminated film is mounted in a display such as a liquidcrystal display, it is preferred that the cross-sectional width of thefilm matches each pixel size in order to suppress a brightnessununiformity among the pixels. The layer B cross-sectional width ispreferably from 10 μm to 1,600 μm, because it is possible to obtain anoptical sheet suitable for pixel sizes of displays including small-sizedisplays used for a portable phone and the like, as well as large-sizedisplays of a 100V type and the like. If the film width is narrower than400 mm, the whole screen of a display having a size of a 32V type orlarger in which a main and high-quality optical sheet is demanded maynot be covered with one film, thereby requiring a plurality of sheets tobe used. This is not preferable in that the manufacturing cost increasesand the brightness ununiformity on the screen may be caused. The filmwidth is more preferably 600 mm or wider, and still more preferably1,200 mm or wider. If the film width is 600 mm or wider, the film can bemounted in a display of a 47V type, and if the film width is 1,200 mm orwider, the film can be mounted in a large liquid crystal display of a90V type or the like. The number of layer Bs takes an important role inexhibiting optical diffusion and collection in an optical sheet. As thenumber of layer Bs increases, a finer optical design can be performedand a more uniform brightness distribution on a screen can be obtainedwhen the optical sheet is mounted in a display. It is not preferred thatthe number of the layer Bs be less than 10 because not only the opticalcharacteristics such as optical diffusion and collection are degraded,but also brightness ununiformity may be caused also when the opticalsheet is mounted in a display. As long as the number of layer Bs is 10or larger, optical diffusion can be given by based on the opticaldiffusion difference between the layers A and B. The number of layer Bsis preferably 500 or more so that optical diffusion and collection canbe provided based on the refraction and reflection at the interfacebetween the layers A and B. More preferably, the number of layer Bshaving a cross-sectional width from 1 μm to 1,600 μm is 500 or larger.

In the laminated film of the present invention, it is preferable that,in the film width direction-thickness direction cross-section, thecross-sectional width of more than half of layer Bs is in a range of anaverage cross-sectional width off ±10 μm. More than half means a numberin excess of a half of the number of layer Bs in the laminated film. Ifthe cross-sectional width of the layer B varies from point to point,there may occur a variation in optical characteristics such as opticaldiffusion and collection, depending on the layout of other constituentelements of a display. However, with the cross-sectional width of morethan half of layer Bs being in a range of the average cross-sectionalwidth of ±10 μM, it becomes possible to suppress a variation in thebrightness distribution on the screen. More preferably, the layer Bwhose cross-sectional width is in the range of the averagecross-sectional width ±10 μm exist continuously in the width directionfor 300 mm or more, in which case a display having no brightnessununiformity on the screen can be obtained also when the film is mountedin a display. Depending on the constitution of the display in which thefilm is mounted, it is also preferable that the cross-sectional width oflayer Bs changes periodically. In cases where light sources are arrangedat a constant interval in such a manner of backlights used for a liquidcrystal display, it becomes possible to diffuse and condense the lightfrom the lamps effectively by periodically changing the cross-sectionalwidth of the layer Bs in accordance with the intervals between thelamps. Especially when the laminated film has a width of not less than400 mm and 10 or more layers B each having a cross-sectional width from0.1 μm to 10,000 μm, the distance between the adjacent layer Bs and thecross-sectional width of the layer A between the adjacent layer Bs arenot limited specifically, and the necessary optical characteristics aredetermined in relation to the design of the peripheral components suchas layout of the light sources of the display in which the film ismounted and the characteristics of other optical sheets. However, it isparticularly preferable that the distance between the adjacent layer Bsis from 10 μm to 200 μM when considering each pixel size of the display.In this case, it is easy to suppress a variation in the opticalcharacteristics among the pixels. The distance P between the adjacentlayer Bs is the distance between the centers of the adjacent layer Bs inthe film width direction. The center of each layer B is determined inthe manner described in JPCA-PE02-05-02S (2007). In the presentinvention, the distance P refers to the center of area gravity of eachlayer B (a cross-sectional width of the layer A between the adjacentlayer Bs is, as in the case of layer B, the maximum length of the layerA in the width direction in a thickness direction-width directioncross-section of the laminated film).

In the laminated film of the present invention, it is preferable thatthe layer Bs exist continuously for 300 mm or more in the widthdirection, wherein the distance P between the adjacent layer Bs at thecenter in the width direction is 0.90 times to 1.10 times as large asthe distance Pc between the adjacent layer Bs at the center in the widthdirection. The distance between the adjacent layer Bs at the center inthe width direction as used herein is the distance between the adjacentlayer Bs across the center in the film width direction in the film widthdirection-thickness direction cross-section. A variation in the distancebetween the adjacent layers B considerably influences the opticalcharacteristics. In this case, however, since the opticalcharacteristics can be controlled at a high precision, it becomespossible to suppress a variation in the brightness distribution on thescreen when the film is mounted in a display. It is more preferable thatthe distance P between the adjacent layers B is 0.95 times to 1.05 timesas large as the distance Pc between the adjacent layers B at the centerin the width direction. In this case, brightness difference does notoccur at any position on the screen. In addition, it becomes possible torealize a large area screen and one film can be mounted in a display of32V type, with the layer Bs existing continuously for not less than 300mm in the width direction, wherein the distance P between the adjacentlayer Bs is 0.90 times to 1.10 times as large as the distance Pc betweenthe adjacent layer Bs at the center in the width direction. As comparedwith a display in which a plurality of width-direction multi-layeredlaminated films are used, it becomes possible to lower the manufacturingcost and suppress the brightness ununiformity on the screen of thedisplay. Further, depending on the structure of the display in which thefilm is mounted, it is also preferable that the distance between thecenters of the adjacent layer Bs changes periodically in the film widthdirection-thickness direction cross-section. In cases where lightsources are arranged at a constant interval in such a manner ofbacklights used for a liquid crystal display, it becomes possible todiffuse and condense the light from the lamps effectively byperiodically changing the cross-sectional width of the layer Bs inaccordance with the intervals between the lamps

In the laminated film of the present invention, it is preferable thatthe thickness of the layer B is from 1 μm to 10,000 μm in the film widthdirection-thickness direction cross-section. The cross-sectional widthof the layer B as used herein refers to the maximum length of the layerB in the thickness direction in the thickness direction-width directioncross-section of the laminated film. If the thickness of the layer B isthinner than 1 μm, since the interface area at which the light impingingon the optical sheet refracts and reflects is small, the opticaldiffusion and collection may hardly be exhibited. If the thickness ofthe layer B is greater than 10,000 μm, since the sheet becomes thick,handling performance may be degraded and the manufacturing cost of thesheet and display may be increased. Further, also when the film ismounted in a display, there is a drawback of, for example, an increasedsize of the display, which becomes problematic. When the thickness ofthe layer B is from 1 μm to 10,000 μm, it becomes possible to provideoptical diffusion and collection while maintaining the handlingperformance. Particularly, when the laminated film is mounted in adisplay, the thickness of the layer B is preferably from 1 μm to 1,000μm, and more preferably from 10 μm to 500 μm. In this case, thelaminated film can be provided with optical characteristics which cansufficiently make the brightness distribution on the screen uniform whenmounted on a display, and in addition, an optical sheet which isexcellent in handling performance with flexibility and can be used in avariety of forms can be obtained.

In the laminated film of the present invention, the thickness of thelayer B is also preferably 0.01 times to 0.5 times as large as the widthof the layer B, in the film width direction-thickness direction crosssection. In this case, it is possible to have a cross-sectional widthcapable of effectively suppressing a brightness variation of backlightsand thinning the film. Preferably, the thickness of the layer B is 0.1times to 0.25 times as large as the width of the layer B. In this case,it is possible to effectively uniformize all of the light beams radiatedfrom the lamps.

In the laminated film of the present invention, as illustrated in FIG.2, the layer B is also preferably covered with a resin (e.g., resin A)in the film width direction-thickness direction cross-section. The layerB covered with the resin corresponds to a state that the side surfacesof the layer B are not exposed except the exposed portion of the layer Bin cases where the layer B is subjected to an exposure treatment at theend of the film. More than half of the layer Bs is preferably coveredwith the resin. With this structure, interlayer stripping at theinterface between different resins becomes difficult to occur.Therefore, the optical characteristics such as optical diffusion andcollection can be maintained even when the film is subjected to bending,stretching and/or impact during manufacture and use, so that a filmhaving excellent durability can be obtained. More preferably, all layerBs are covered with the resin, so that a change in the opticalcharacteristics caused by bending, stretching or impact duringmanufacture and use can be almost suppressed.

In the laminated film of the present invention having the layer Bscovered with resin, the thickness of the resin covering the layer B ispreferably from 5 μm to 1,000 μm in the film width direction-thicknessdirection cross-section. The thickness of the resin covering the layer Bas used herein is the minimum value of the distance between theinterface of each and the film surface in the thickness direction, andis preferably from 5 μm to 1,000 μm. The influence of bending,stretching or impact during manufacture and use can be alleviated by theresin covering the layer B, and this effect becomes prominent when thethickness of the resin covering the layer B is 5 μm or thicker. Further,if the thickness of the resin covering the layer B is 1,000 μm orthicker, the film flexibility may be degraded; however, by setting thethickness at 1,000 μm or thinner, it becomes possible to suppressdegradation in the optical characteristics caused by bending, stretchingand impact while maintaining a good flexibility, and the interfacebetween the layers A and B actually related to the opticalcharacteristics such as optical diffusion and collection is notinfluenced, so that excellent durability can be exhibited.

In the laminated film of the present invention, the film thickness ispreferably from 1 μm to 1,000 μm. The film thickness as used herein isan average value of film thicknesses in the film width direction. If thefilm thickness is from 1 μm to 1,000 μm or thinner, the film hassufficient flexibility, so that not only the handling performance isexcellent, but also the film can be installed on a flat surface as wellas on a deflected surface; therefore, the method of using such film canbe broadened in a variety of manners.

Depending on a display, a preferred film thickness is from 1,000 μm to10,000 μm. In this case, it becomes possible to provide the laminatedfilm with a function as a substrate to retain other optical sheetsmounted in the display in the same manner as a conventional diffusionplate, in addition to the desired optical characteristics such opticaldiffusion and collection. Therefore, the structure of the display can besimplified, and thinning and weight reduction of the display andsuppression of an increase in the manufacturing cost can be attained.

The shape of the layer B of the present invention is not limitedspecifically, and may be circle, ellipsoid, semicircle, and a polygonsuch as a triangle, a tetragon, a trapezoid, a parallelogram, a pentagonor a hexagon. According to the method described later, a variety ofshapes of the layer B can be realized easily. Corners of such polygonare not required to be strict corners, but may also be curved corners.Particularly, in the laminated film of the present invention, the shapeof the layer B is preferably asymmetric relative to the center axis ofthe layer B in the thickness direction in the film thicknessdirection-width direction cross-section. The center axis in thethickness direction as used herein is a straight line positioned at anequal distance from the apexes of the upper surface side and the lowersurface side of the layer B cross-section in the thickness direction andat the same time, parallel to the film plane. In cases where the layer Bis symmetric relative to the center axis in the thickness direction, thelight impinging on the laminated film uniformly exhibits opticaldiffusion and collection in the film. On the other hand, in cases wherethe shape of the layer B is asymmetric relative to the center axis inthe thickness direction, since the optical path length and the incidenceangle of the impinging light to the interface on each layer change withthe light incidence position, it becomes possible to create a differencein the optical diffusion and collection between layers, thereby enablingto provide more uniform optical characteristics. In a preferredembodiment, the shape of the layer B is a triangle, a parallelogram, atrapezoid and a semicircle. In these shapes, the interface between thelayers A and B is tilted in relation to the film surface and arranged insuch a manner that the optical path length is changed with the lightincidence position. Therefore, there is an increase in the ratio of thelight, which changes its traveling direction upon refraction andreflection at the interface between the layers A and B, to the lightimpinging on the surface, as well as in the degree of optical diffusionin the optical path changes, thereby allowing the film to exhibitprominent optical diffusion and collection. In the laminated film of thepresent invention, it is also preferable that S1 is not greater than 0.8times of S2, wherein S1 and S2 (S1<S2) are cross-sectional areas of thelayer B halved by the center axis in the thickness direction. Comparedto cases where the S1 is in the shape of for example, a tetragon, arectangle or a parallelogram, which is larger than 0.8 times of the S2,as the S1 has a shape having a more prominent asymmetricity relative tothe center axis, such as a semicircle or a triangle, it becomes easierto increase the inclination degree of the layer B interface and give adifference in the optical path length of the light impinging the layerB, so that optical diffusion and collection can be improved further. Oneof the characteristics of the laminated film of the present inventionresides in that the film can optionally be formed into a complicatedshape unable to be formed by a copy method such as imprint andphotolithography. Also, in the laminated film of the present invention,it is preferable to form irregularities on the film surface. In ageneral flat surface film, regardless of the position of the lightimpinging on the film surface, as long as the incidence angle is thesame, all of the impinged lights are reflected at the air-film interfacein the same manner and enter the film at a particular angle. Incontrast, when the film surface is irregular, even if light is impingedon the film surface at the same incidence angle, the light enters thefilm at a different refraction angle since the inclination on the filmsurface varies with the position on the film. Similar to the incidencesurface, light is output in various directions from the output surfacebecause the inclination on the film bottom surface varies with itsposition. Therefore, the light impinged on an irregular film is outputin various directions relative to the incidence angle, thereby allowingthe film to exhibit a high optical diffusion and enabling to provide thefilm with a high optical diffusion when used as a diffusion film.Similarly, by controlling the irregular shape, the same effect as thatof a lens can be given to the film, allowing the laminated film to havea high optical collection. Examples of the method of forming theirregular shape include an embossing process and an edging process of alaminated film.

In the laminated film of the present invention, it is preferable thatone of the resins A and B is insoluble to a solvent to which the otheris soluble. In such laminated film, the layers A and B can be separatedor the layer A or B can be exposed by immersing the end portion of thefilm into a particular solvent. Therefore, when the laminated film isused as an optical sheet such as a diffusion film or a light collectionfilm, an irregular surface can be formed easily by treating with asolvent, so that optical diffusion and collection performances can alsobe improved. In the present invention, being soluble to a solvent meansa condition in which the weight of a solid resin, which is formed byimmersing a resin in a solvent for one day at a temperature for carryingout a dissolution process and subsequently drying the resin thusobtained and collected from the solvent, becomes not more than 50% ofthe weight of the resin prior to the immersion in the solvent. Examplesof a resin having a high solubility to a solvent and high transparencyinclude acrylic resins and polystyrenes. By using a combination of theseresins and a resin having an inferior solubility such as polyester orpolycarbonate, it is possible to perform a separation process andsurface treatment on the film using a solvent.

In cases where the laminated film of the present invention ismanufactured by a continuous process, the laminated film can be providedin the form of a film roll. When the laminated film can be provided as afilm roll, various processings of the film surface can be performed in aroll-to-roll manner, so that a surface-treated film can be manufacturedat a lower cost.

In the film roll of the present invention, the winding hardnessvariation in the width direction is preferably from 0.0001 to 6. Ahardness variation in the width direction refers to a difference betweenthe maximum and minimum hardness values when the winding hardness ismeasured at five points in a film roll width of 400 mm. In the laminatedfilm of the present invention, the surface irregularity caused by thewidth-direction multi-layered laminated structure is likely to beformed, and when such film is wound into a roll shape, there occurs aproblem that a laminated film having defective flatness is likely to beformed because of the surface irregularity. However, if the windinghardness variation in the roll width direction is from 0.0001 to 6, itis possible to obtain a laminated film having excellent flatness.Examples of the method of setting the winding hardness variation in theroll width direction in a range from 0.0001 to 6 include a method ofrolling a protective film while laminating the film.

The laminated film thus obtained can be used as a diffusion film andlight-collecting film suitable for a display or the like, and thelaminated film of the present invention can be utilized also forapplications other than these, the details of which will be describedbelow.

The laminated film of the present invention is suitable for use as aviewing angle control film. By using a resin with excellent translucencyas the resin A and a resin with light-shielding property as the resin B,the light that impinges on the film perpendicularly to the surface istransmitted, but the light that impinges on the surface of the film atan angle smaller than a certain angle is absorbed by the B layer Bs andnot transmitted. Therefore, by arranging the film at the surface of adisplay or the like, the viewing angle can be controlled. The embodimentpreferable for use as a viewing angle control film will be especiallydescribed below with respect mainly to the differences from the abovedescription.

In cases where the laminated film of the present invention is used as aviewing angle control film, in particular, the resin A and/or the resinB is preferably polyester resin in view of the price, heat resistance,transparency, and strength.

In cases where the laminated film of the present invention is used as aviewing angle control film, in particular, at least one of the layerspreferably contains particles having light-shielding property. In thiscase, the light-shielding property can be given to one of the layers,thereby allowing for shielding of transmission of the light thatimpinges on the film at an angle not smaller than a certain angle.Examples of such particles include carbon black, iron black (triirontetroxide), a black titanium pigment, and perylene pigment/dye. Carbonblack is particularly preferable in view of the high dispersity inresins and high masking ability.

In cases where the laminated film of the present invention is used as aviewing angle control film, it controls the viewing angle by utilizingthe light shading property of the layer B. Thus, in the laminated filmof the present invention, the difference between the refractive index ofthe resin A (na) and that of the resin B (nb), |nb−na|, is preferablyless than 0.002. With the refractive index difference between the resinA and the resin B of 0.002 or more, light refraction and reflectionoccur at the interface and images through the film can look distortedfrom some angles. Examples of the method of obtaining a refractive indexdifference |nb−na| less than 0.002 include a method in which the resin Bthat is substantially the same as the resin A is used as a repeatingunit and particles having light-shielding property are added thereto.

The laminated film according to an exemplary embodiment of the presentinvention has a width of 400 mm or more and the number of layer Bshaving a cross-sectional width of not less than 0.1 μm and not more than10,000 μm is 10 or more; however, in particular, in cases where thelaminated film of the present invention is used as a viewing anglecontrol film, the cross-sectional width of the layer B is preferably notless than 1 μm and not more than 100 μm. If the cross-sectional width ofthe layer B is less than 1 μm, depending on the light-shading propertyof the resin B, the light that impinges on the layer B may not becompletely absorbed and viewing angle control ability may not be fullyexhibited. If the cross-sectional width of the layer B is more than 100μm, the layer Bs may be clearly recognized also when the screen isviewed from the front, and it may not be suitable for being mounted on adisplay. If the cross-sectional width of the layer B is not less than 1μm and not more than 100 μm, sufficient viewing angle control abilitycan be exhibited while maintaining good screen visibility from thefront. If the width of the film is less than 400 mm, one film cannotcover the entire screen of a display with a size of 32V or more, inwhich viewing angle control films are mainly used, and it becomesnecessary to use multiple films to be mounted. This may cause anincreased manufacturing cost and ununiformity of the viewing anglecontrol ability, which is not preferred.

In cases where the laminated film of the present invention is used as aviewing angle control film, in the film width direction-thicknessdirection cross-section, it is particularly preferred that the thicknessof the layer B be not less than 1 μm and not more than 1,000 μm. If thethickness of the layer B is less than 1 μm, the area of the layer B bywhich the incident light is absorbed is so small that the controllableview angle may be small. If the thickness of the layer B is more than1,000 μm, the thickened sheets may cause impaired handling property(e.g., it can be handled only in the form of a plate), an increasedmanufacturing cost of the sheets and the display on which the sheets tobe mounted, and a problem of an increase in the size of the display whenthe sheets are mounted on the display. With the thickness of the layer Bof not less than 1 μm and not more than 1,000 μm, the viewing anglecontrol ability can be given while maintaining the ease of handling. Amore preferred thickness of the layer B is not less than 10 μm and notmore than 200 μm, in which case, when the sheet is mounted on thedisplay, flexibility, improved ease of handling, and thinning and weightsaving of the display can be achieved.

In cases where the laminated film of the present invention is used as aviewing angle control film, the distance between the adjacent layer Bsis determined based on the cross-sectional width of the layer B, thethickness of the layer B, and the desired viewing angle. However, toachieve simultaneously the viewing angle control ability and thevisibility of a transmitted image viewed from the front, the ratio ofthe thickness of the layer B to the cross-sectional width of the layer Bis preferably 1 or more. To maintain the screen visibility from thefront, it is preferred that the distance between the adjacent layer Bsbe large and the cross-sectional width of the layer B be small, on theother hand, larger thickness of the layer B can give high viewing anglecontrol ability even if the distance between the layer Bs is increased.As long as the ratio of the thickness of the layer B to thecross-sectional width of the layer B is 1 or more, high view anglecontrol ability can be given while maintaining the visibility from thefront. The ratio of the thickness of the layer B to the cross-sectionalwidth of the layer B is more preferably 5 or more, and still morepreferably 10 or more. The shape of the layer B is preferably rectanglewith the thickness direction as the long side.

In cases where the laminated film of the present invention is used as aviewing angle control film, the film thickness is preferably not lessthan 1 μm and not more than 1,000 μm. The film thickness as used hereinrefers to a mean value of the film thickness distribution in the widthdirection of the film. As long as the film thickness is not less than 1μm and not more than 1,000 μm, the film will have flexibility sufficientfor a film, so that not only an improved ease of handling is obtained,but also it can be placed on a curved portion as well as on a flatplane; therefore, its use can be diversified.

In cases where the laminated film of the present invention is used as aviewing angle control film, the film is particularly preferably aquadrangle such as a rectangle or trapezoid. Films of these shapeseasily transmit the light from the front well and also can improve theproperty of shading the light that impinges on the film at a certainangle.

In cases where the laminated film of the present invention is used as aview angle control film, the film surface is preferably smooth. If thefilm surface is irregular, when the film is mounted on a display, it maybe hard to recognize displayed images because the angle of refractionand reflection of the light that impinges on the film varies; however,if the film surface is smooth, the displayed images can be recognizedwell regardless of the position of the observer or the angle.

The laminated film of the present invention is suitable for use as anoptical waveguide film. By using, as the resin B, a resin whoserefractive index is higher than that of the resin A, light-guidingproperty can be given to the light that impinges on the layer B from awidth direction-thickness direction cross-section by repeating totalreflection at the interface between the layer A and the layer B.

The laminated film of the present invention is suitable as an opticalmodule. The term “optical module” generally means an electric part whichconverts light to electricity and vice versa. For example, it is asystem having a basic constitution of vertical cavity surface emittinglaser (VCSEL) which is the side of transmitting light-optical waveguidefilm which is a polymer optical waveguide path-photodiode which receiveslight. More specifically, for example, it is a system in which thisconstitution is mounted in an optical-magnetic card, in an opticalbackplane for interconnecting devices, between memory CPUs, or on thepackage of a switch LSI.

The laminated film of the present invention is suitable for a lightguide, an illumination apparatus, and a display using an illuminationapparatus. The film may be used as a solar cell member, for example, byguiding light, with almost no attenuation even in a long-distanceoptical transmission thanks to its high optical waveguide property, tosolar cells by interconnecting a core with a Fresnel lens and collectingsolar light. By employing red, blue, yellow and green light as thesource of the light to be guided, the film may be used for ornamentaluses. Further, the film may be used as an illumination member by takingthe light such as those from a halogen lamp, LED, sun light or the like,waveguiding the light to the desired site through the film, andradiating the light. Such illumination member may be widely used as anillumination member for LCD backlight, machines for moving such as anautomobile, airplane and ship, and building materials for a residence,factory, office and the like, exerting effects such as an improvedbrightness and energy saving.

The laminated film of the present invention can be suitably used as acommunication apparatus or an optical waveguide for short to middle/longdistance communication such as inter-device communication orintra-device communication. In this case, it may also be preferably usedfor a light guide with a connector. As the standard of the connector, inview of the versatility of the multicore-type plastic, MT connector, MPOconnector, MPX connector, PMT connector or the like is preferably used.

The embodiment preferable for use as an optical waveguide film will beespecially described below with respect mainly to the differences fromthe above description.

In cases where the laminated film of the present invention is used as anoptical waveguide film, since the film is required to exhibit a highstrength, heat resistance, and transparency and to prevent propagationloss when the light is guided through the sheet, the film is preferredto be polycarbonate; polymethylmethacrylate; cyclic olefin copolymerwhich is a copolymer between norbornene and ethylene copolymerized bymetallocene or a Ziegler-Natta catalyst; cyclic polyolefin obtained byring-opening metathesis polymerization and hydrogenation of anorbornene-based monomer; polyimide resin; poly (4-methylpentene-1);polyethylene terephthalate; polystyrene; or fluorinated polymer.Further, to reduce the propagation loss, it is more preferred that thehydrogen atoms in the polymer be deuterated.

In cases where the laminated film of the present invention is used as anoptical waveguide film, it is preferred that the refractive index of theresin B (nb) be higher than the refractive index of the resin A (na) andthe difference between the refractive indices, nb−na, be 0.001 or more.With the refractive index of the resin B being higher than therefractive index of the resin A, light can be guided through the resinB; however, if the difference between the refractive indices, nb−na, isless than 0.001, the reflection at the interface between the resin A andthe resin B becomes so weak that sufficient light-guiding property maynot be given. In an optical waveguide film for communication uses, thedifference between the refractive indices, nb−na, should be arbitrarilyselected depending on the wavelength of the light, the connectors, thenumber of modes or the like. In cases where the film is used as anillumination member, the difference is preferably 0.010 or more, morepreferably 0.030 or more, and most preferably 0.06 or more, and thelight-guiding property improves as the difference between the refractiveindices increases, allowing for light transmission with almost noattenuation of the light intensity.

The laminated film according to an embodiment of the present inventionhas a width of 400 mm or more and the number of layer Bs having across-sectional width of not less than 0.1 μm and not more than 10,000μm is 10 or more. In particular, in cases where the film is used as anoptical waveguide film, the cross-sectional width of the layer B ispreferably not less than 10 μm and not more than 5,000 μm. In this case,the connection to peripheral equipment such as connectors becomes easywhile maintaining sufficient light-guiding property. In cases where theoptical waveguide film is used as illumination parts, it is preferredthat the width of the film be 400 mm or more and the number of layer Bsbe 10 or more, and more preferred is 500 or more. In this case, whenused for communication uses, it can be used as multichannel wiring witha large capacity, and an enhanced convenience, e.g., cutting out only arequired width from one film to use, is obtained.

In cases where the laminated film of the present invention is used foran optical waveguide film, in the film width direction-thicknessdirection cross-section, more than half of the layer Bs' cross-sectionalwidths are preferably in the range of the average cross-sectional width±10 μm. If the cross-sectional width of the layer B varies from point topoint, variation in the optical waveguide performance of each layer Bmay occur. However, if more than half of the layer Bs' cross-sectionalwidths are in the range of the average cross-sectional width ±10 μm,variation in the optical waveguide performance can be prevented. Morepreferably, the layer B whose cross-sectional width is in the range ofthe average cross-sectional width ±10 μm exist continuously in the widthdirection for 300 mm or more, in which case variation in the opticalwaveguide performance of almost all the layer Bs on the film can beprevented. In addition, the cross-sectional width of the layer B isassociated with the luminescence intensity when the film is used as anillumination member; however, the continuous existence of the layer Bwhose cross-sectional width is in the range of the averagecross-sectional width ±10 μm in the width direction for 300 mm or moreallows for the uniformity of the luminescence intensity of the film inthe width direction.

In cases where the laminated film of the present invention is used foran optical waveguide film, the distance between the adjacent layer Bs ispreferably not less than 10 μm and not more than 2,000 μm, andespecially preferably not less than 10 μm and not more than 500 μm. Asthe distance between the adjacent layer Bs decreases, multichannel canbe achieved in a smaller area.

In cases where the laminated film of the present invention is used foran optical waveguide film, the layer Bs, wherein the distance betweenthe adjacent layer Bs, P, is 0.90 times to 1.10 times as large as thedistance between adjacent layer Bs at the center of the film in thewidth direction, Pc, preferably exist continuously in the widthdirection for 300 mm or more. Since the optical waveguide film is usedin connection to connectors for the input/output of the light, thedistance between the layer Bs used for optical waveguiding is preferablyconstant, and a wide variation in the distance between the adjacentlayer Bs can make it impossible to connect the film to the connectors orcontrol the input/output correctly. If the distance between the adjacentlayer Bs, P, is 0.90 times to 1.10 times as large as the distancebetween the adjacent layer Bs at the center of the film in the widthdirection, Pc, the distance between the layer Bs can be maintainedalmost constant, thereby allowing for easy and normal connection to theconnectors. In addition, when the film is used as an illuminationapparatus, the distance between the adjacent layer Bs, P, is morepreferably 0.95 times to 1.05 times as large as the distance between theadjacent layer Bs at the center of the film in the width direction, Pc,in which case the connection to the connectors can be performed withalmost no problem. Further, if the layer Bs, wherein the distancebetween adjacent layer Bs, P, are 0.90 times to 1.10 times as large asthe distance between adjacent layer Bs at the center of the film in thewidth direction, Pc, exist continuously in the width direction for 300mm or more, a film having a larger area can be obtained. Furthermore,when the film is used as an illumination apparatus, variation in thedistance between the adjacent layer Bs causes illuminance ununiformityin the irradiated light; however, if the layer Bs, wherein the distancebetween the adjacent layer Bs, P, is 0.90 times to 1.10 times as largeas the distance between adjacent layer Bs at the center of the film inthe width direction, Pc, exist continuously in the width direction for300 mm or more, the illuminance in the width direction of the film canbe uniformized.

In cases where the laminated film of the present invention is used foran optical waveguide film, in the film width direction-thicknessdirection cross-section, it is particularly preferred that the thicknessof the layer B be not less than 10 μm and not more than 2,000 μm. If thethickness of the layer B is less than 10 μm, it may lead to poorintroduction of light into the layer Bs and poor connectivity withconnectors or the like. If the thickness of the layer B is more than2,000 μm, thickened film may cause impaired handling property (e.g., itcan be handled only in the form of a plate) to limit the use. If thethickness of the layer B is not less than 10 μm and not more than 2,000μm, high optical waveguide performance and good connectivity withconnectors or the like can be given while maintaining the ease ofhandling. For the same reason, the thickness of the film also ispreferably not less than 10 μm and not more than 2,000 μm.

In cases where the laminated film of the present invention is used foran optical waveguide film, the layer B, wherein the cross-sectional areaof the layer B in a width direction-thickness direction cross-section(cross-sectional area A) is 0.90 times to 1.10 times as large as thecross-sectional area of layer B located at the center of the film in thewidth direction (cross-sectional area Ac), is preferably continuouslyexist in the width direction for 300 mm or more. The cross-sectionalarea of the layer B has an effect on the optical waveguide performance;however, if the cross-sectional area A is 0.90 times to 1.10 times aslarge as the cross-sectional area Ac, variation in the optical waveguideperformance of the layer B can be prevented. The cross-sectional area Ais more preferably 0.95 times to 1.05 times as large as thecross-sectional area Ac, in which case the optical waveguide performanceof each layer B is substantially uniform, and this is preferable formultichannel optical waveguide. In addition, the continuous existence ofthe layer B for 300 mm or more whose cross-sectional area A is 0.90times to 1.10 times as large as the cross-sectional area Ac allows forthe uniformity of the performance in almost all channels.

In cases where the laminated film of the present invention is used foran optical waveguide film, for a communication member, in view of thefact that mode dispersion and propagation loss depending on the coreshape occur, a shape having a symmetry about the center of the core ashigh as possible is preferred, and the most preferred shape is circular.Desirable symmetry includes line symmetry and point symmetry. Forillumination use, in view of increasing the luminescence area and makingthe brightness of the surface uniform, a shape which is flat in thewidth direction is preferred, and the most preferred shape is rectanglewith the thickness direction as the long side.

In cases where the laminated film of the present invention is used foran optical waveguide film, it is also preferred that the layer B becovered with resin in a width direction-thickness directioncross-section. More than half of the layer Bs are preferably coveredwith resin. Such structure makes it unlikely for interlayer peeling atthe interface between different resins to occur, and, in addition, canprevent light leakage from the layer B due to scratches on the surfaceof the layer B used for optical waveguiding, thereby providing a filmthat can maintain an optical waveguide performance and has an excellentdurability. It is more preferred that all of the layer Bs be coveredwith resin, in which case a decrease in the optical waveguideperformance can be substantially prevented. On the other hand, when thefilm is used as an illumination member, structure in which one side ofthe film is not covered with resin is also preferable. With the filmbeing not covered on one side, light leaks from the uncovered side toallow for its use as plane illumination, and in addition, variousnecessary processings can be applied directly to the layer B, resultingin an improved processability.

In cases where the laminated film of the present invention is used foran optical waveguide film, a part of the end portions of the film ispreferably branched. “End portions of the film are branched” means astate in which at least one end portion of the laminated film isbranched in plurality. Examples of the method of branching include amethod of branching mechanically by microslits or the like and a methodof branching by dissolving with a solvent a part of the covering resin Aand exposing a part of the layer B. If a part of the end portions of thefilm is branched, an easy connection to an individual light sourcearranged scatteredly, e.g., LED light source, or to a point light sourcewith the branched film end portion in the form of a bundle can beachieved.

In cases where the laminated film of the present invention is used foran optical waveguide film, it is also preferred that irregularities beprovided to the surface of the film. By providing the irregularities tothe surface of the film, light can leak from the concave portions andthe film can be used as a plane light source. More preferably, theirregularities reach the layer B, in which case the light can leak fromthe layer B more effectively and the brightness can be enhanced.

Next, description will be made of a preferred method of manufacturingthe laminated film of the present invention. Two kinds of resins, resinA and resin B, are prepared in the form of a pellet; however, they arenot necessarily in the form of a pellet. When a blend of a plurality ofresins and additives is used as the resin A or resin B, it is preferablethat a resin which is compounded by a biaxial extruder or the like inadvance and pelleted is used. By using a pellet compounded beforehand,it is possible to obtain a film containing resins and additivesuniformly dispersed. The pellet is dried in advance in hot blow or undervacuum if necessary to be thereafter supplied to an extruder. The resinsheated and melted in the extruder are extruded at a constant amount by agear pump or the like, and a filter or the like removes foreign matters,denatured resin or the like.

The resins fed from two or more extruders via different flow paths arethen supplied to an extrusion die. Either a uniaxial extruder or abiaxial extruder may be used without any problem. Particularly, if aplurality of resins and additives blended together are used as the resinA and the resin B, such resins and additives can be dispersed uniformlyby using a biaxial extruder. In this case, the screw structure becomesvery important. For example, in alloying, Dulmadge-type screw andMuddox-type screw are preferable for a single screw, and a screwstructure in which paddles are combined in such a way that an enhancedkneading power is obtained is preferable for a twin screw. On the otherhand, when only one kind of thermoplastic resin is extruded from oneextruder, since a foreign matter is generated which is a cause of apropagation loss when the kneading is too strong, a single screwextruder using a full flight screw is preferable. The L/D of the screwis preferably 28 or less, and more preferably 24 or less. Thecompression ratio of the screw is preferably 3 or less, and morepreferably 2.5 or less. As a method of eliminating a foreign matterwhich causes propagation loss, a known technique such as vacuum ventextrusion or use of a filtration filter is effective. The pressure ofthe vacuum vent is preferably about 1 to 300 mmHg in terms ofdifferential pressure. A high precision filtration can be performed byusing a FSS (Fiber Sintered Stereo) leaf disc filter as the filtrationfilter during melt extrusion. It is preferable that filtering precisionof the filter is changed as appropriate depending on how large or howmuch the foreign matters occur and depending on the filtration pressurebased on the resin viscosity; however, it is preferred to use a filterhaving a filtering precision of 25 μm or less. It is more preferred touse a filter having a filtering precision of 10 μM or less, and it isstill more preferred to use a filter having a filtering precision of 5μm or less. At this time, in view of decreasing the leakage of resin,the resin pressure at the tip of the extruder is preferably 20 MPa orless, more preferably 10 MPa or less.

A preferable example of the extrusion die of the present invention isillustrated in FIGS. 3 to 5. FIG. 3 illustrates plan views of an exampleof the extrusion die of the present invention showing disassembledelements thereof viewed from the top surface side. FIG. 4 is aperspective view of an element 6. FIG. 5 is a cross-sectional view of anextrusion die 10 with integrated elements 3 to 9. The gray portion inFIG. 5 indicates a flow path of the resin A, and the black portionindicates a flow path of the resin B. By using such an extrusion die, itbecomes easy to provide a width-direction multilayer laminated filmhaving a large area and uniform optical properties.

Next, each component of the extrusion die will be described withreference to FIGS. 3 to 5. Reference numeral 3 represents a resin inletsection in which flowed resin A and resin B are expanded in the widthdirection. In FIG. 3, the upper and lower holes are inlet ports for theresin A, and the central hole is an inlet port for the resin B. Theresin inlet section constitutes a portion of a manifold section.Reference numeral 4 represents the manifold section. Reference numeral 5represents a first slit section whereat the flow paths are compressed inthe width direction to uniformize the flow rate of the resin A and theresin B in the width direction. Reference numeral 6 represents a nozzlesection having a structure in which a plate section for fractioning theresin B into each layer B and nozzles 11 are integrated. The nozzle 11is a straight tube extending from the plate portion illustrated in FIG.4 to the downstream side. The resin B is guided to a junction 8 via thenozzles, while the resin A flows through the slit section arranged aboveand under the nozzles. Reference numeral 7 represents a second manifoldsection whereat the resin As flowing separately in two flow paths arejoined together. Reference numeral 8 is a junction having hole 14 s intowhich the nozzles extend from the nozzle section 6. The size of the hole14 is set larger than the outer shape of the nozzle section, so thatresin A can flow through a space between the hole 14 and nozzle outerwall and, thereby allowing the resin A to cover or sandwich the resin Bin the hole. Although not shown, a runner may be provided from thenozzle outer wall to hole inner wall for position alignment of thenozzle 11 s in the hole 14. The nozzle 11 is preferably inserted toabout a half of the junction 8. Reference numeral 9 represents a secondslit section whereat the resin A and the resin B are joined together ateach hole 14 into a sheet shape. It is preferable that the second slitsection is constituted of two members or four or more members. A slightvariation in gaps between slits may cause optical irregularity in thewidth direction in a large area; therefore the members of the secondslit section is required to have a particularly high precision.

In order to obtain a target shape of the layer B, a design of thecross-sectional shape of the hole of the nozzle 11 is required toconsider elongation deformation after ejection from the extrusion die.Since elongation deformation of a wide film elongates in the planedirection in many cases, a design is desired considering compression inthe width direction is preferred. Namely, even if the cross-sectionalshape of the hole of the nozzle 11 is set circular, a laminated layerejected out of the extrusion die is expanded in the plane direction andcompressed in the thickness direction, so that the layer B of theobtained film has an ellipsoidal shape having a longer axis in the widthdirection. If the shape of the layer B is desired to be circular, withconsideration of elongation deformation after the ejection from theextrusion die, the hole of the nozzle 11 is preferably set to have anellipsoidal shape having a longer axis in the thickness direction. Thisprinciple is obviously applicable not only to the case of a circularcross-section of the layer B, but also any shape of the layer B.

Various shapes are applicable to the cross-sectional shape of the holeof the nozzle 11, including circular, ellipsoidal, and semi-circularshapes, and polygonal shapes such as triangular, tetragonal,trapezoidal, pentagonal and hexagonal shapes. The extrusion die to beused particularly for forming a laminated film of the present inventionhas preferably a nozzle asymmetrical to the center axis in the widthdirection. The center axis in the width direction used herein refers toa straight line which is parallel to the alignment direction of the hole14 s and is positioned at an equi-distance from the apexes of the upperand lower sides of each nozzle in the width direction. By using suchnozzle, it becomes possible to obtain a laminated film whose layer B isasymmetrical to the center axis in the width direction. A shape such asa tetragonal shape having a very long side may also be formed byarranging circular and tetragonal nozzles adjacent to each other to joinresins B together at the junction. If such an extrusion die is used, thenumber of layer Bs can be adjusted by the number of nozzles. Further,the cross-sectional width of the layer B can be adjusted by a nozzleshape and an ejection amount.

It is preferable that the nozzle 11 s are arranged in the widthdirection and that the nozzles are provided at the nozzle section 6 in anumber as many as or more than the number of layer Bs of a desiredlaminated film. By assigning one nozzle to each layer B, it becomespossible to manufacture the layer Bs having a cross-sectional shapecontrolled highly precisely in a number as many as the number ofnozzles, and to obtain a laminated film having a large area and uniformoptical properties. The number of the nozzles is preferably 10 or largerin the width direction, more preferably 250 or larger, still morepreferably 500 or larger, and still more preferably 1,000 or larger.

In addition to such layout of the nozzles arranged in one row in thewidth direction, a layout having a plurality of rows also in the filmthickness direction is applicable as well. In the latter case, aplurality of rows of the layer Bs can also be laminated in the thicknessdirection of the thus obtained laminated film. Since a variety ofoptical designs are possible, it becomes possible to further improve theoptical properties.

It is advantageous to uniformize the flow rates of the resin Bs flowedout from each of the nozzle 11 s in order to obtain a width-directionmultilayer laminated film having uniform optical properties. The flowrate of the resin B flowed out of each nozzle 11 is proportional to apressure drop of fluid in the nozzle 11 defined by the nozzle diameterand the nozzle length. For the extrusion die of the present invention,therefore, it is preferable that the diameters and lengths of all nozzle11 s are uniformized in order to suppress a variation in thecross-sectional areas and shapes. Further, if a viscosity changeassociated with the share rate is large, a difference becomes smallbetween a pressure drop in a nozzle having a higher share rate comparedto other flow paths and a pressure drop in the second slit section andother flow paths, and the flow rate of the resin B from the nozzle maybe reduced at the opposite end portions in the width direction. In thiscase, by increasing the diameters of the nozzles at the opposite endportions to slightly larger than those of the nozzles positioned in thecentral area in the width direction, the flow rates of the resin Bs fromthe nozzles can be uniformized. In this manner, by uniformizing the flowrates of the resins Bs from the nozzles, also in the obtained laminatedfilm, it becomes easy to attain uniform cross-sectional area and shapesof layer Bs.

It is also advantageous to uniformize the flow rates in the widthdirection at the first slit section. By uniformizing the flow rates ofthe resin Bs in the width direction at the first slit section, the flowrates of the resin Bs to the nozzles arranged in the width direction arefurther uniformized and it becomes easy to obtain a film having uniformcross-sectional widths of the layer Bs in the obtained laminated film aswell. Therefore, in the extrusion die of the present invention, it ispreferable to provide a manifold on the upstream side of the first slitsection.

Each of the nozzle 11 s arranged in the width direction extends into thehole 14. By having such constitution, it is possible to guide the resinA in such a manner to surround the resin B in each hole, therebyenabling to attain a high lamination precision by laminating laminationflows in the same number as the number of nozzles. Consequently, itbecomes possible to obtain a laminated film having a large area anduniform optical properties. The distal end of the nozzle 11 on the sideof the junction 8 extends preferably only to an upstream position of theoutlet of the hole at the junction 8. In this case, the resin B flowedout of the nozzle 11 is laminated with the resin A in the hole 14, andthereafter the flow can be stabilized in the hole 14; therefore, achange in the cross-sectional shape of the resin B flowed out of thenozzle 11 can be suppressed to a minimum.

By using the nozzle 11 surrounded by the hole 14 s in this manner, thelayer Bs flow to the junction in the form covered with the layer A. Itbecomes therefore possible to easily laminate the layer Bs in a desirednumber of layers. In addition, by controlling the flow rates of thelayers A and B, it becomes possible to form films having a variety ofcross-sectional shapes even with a single extrusion die.

When a plurality of nozzles are used in order to obtain a shape such asa tetragonal shape having a very long side, it is also preferable toinsert a plurality of nozzles into one fine hole 14. In this case, byallowing the resin Bs flowed out of a plurality of nozzles to be joinedin the hole 14 and formed into a shape of a layer, it becomes easier toobtain a desired shape at a high precision.

In order to maintain the shape of the layer B at constant, it isadvantageous that the flow rates of the resin As flowed out of the hole14 are also uniform in the width direction. There is a possibility thatthe shape of the layer B flowed out of the nozzle 11 is deformed by theflow of the resin A in the hole 14. It is therefore preferable that thediameters and lengths of the hole 14 s are also made uniform, becausethe flow rate is controlled by the diameter and length of the hole 14 inthe same manner as in the case of the nozzle.

Although the cross-sectional shape of the hole 14 may also take avariety of shapes, a particularly preferable shape is tetragonal. Inthis case, it becomes possible to suppress a change in a fluid flow to aminimum when the resins flowed from the nozzles are joined, therebyenabling to maintain the shape of the layer B which is the same as thenozzle shape. Meanwhile, it is also preferable that the shape of thehole 14 is analogous to the nozzle shape. In this case, it becomespossible to suppress a change in the cross-sectional shape of the resinB to a minimum when the resin B flowed out of the nozzle is laminatedwith the resin A in the hole 14.

Further, the hole 14 is preferably asymmetrical relative to the centeraxis in the thickness direction. The center axis in the thicknessdirection used herein refers to a straight line which is parallel to thealignment direction of the hole 14 s and is positioned at anequi-distance from the apexes of the upper and lower sides of eachnozzle in the width direction. By using such holes, the resin extrudedfrom the nozzle can be easily deformed into an asymmetrical shaperelative to the center axis in the thickness direction, so that alaminated film having the layer B asymmetrical to the center axis in thethickness direction can be obtained. In order to obtain awidth-direction multi-layered laminated film of a large area havinguniform characteristics, it is important not to perform width expansionand compression in the path from the junction 8 to the second slitsection 9, as much as possible. By applying the width expansion andcompression in the flow path after the junction, the flow ratedistribution changes due to deformation of the flow path, and the shapeof the laminated flow obtained by laminating resins exactly followingthe design is deformed. As a result, the obtained laminated film alsohas a cross-sectional shape different from the designed shape, so thatthe desired characteristics may not be obtained and the characteristicsin the width direction may be changed. If it is necessary to performwidth expansion and compression, the laminated flow is preferablydeformed in an analogous manner. The analogous manner used herein refersto a deformation in such a manner that the same ratio between the widthdirection length and the thickness length is maintained. In cases wherethe flow path is deformed in such analogous manner, although the flowrate in the flow path changes, since the flow rate changes in the flowpath at a uniform ratio, the shape of the laminated flow laminated atthe junction becomes not likely to be changed.

It is also preferable that the flow path length from the junction 8 tothe outlet of the second slit section 9 is made as short as possible. Asthe flow path length after the junction becomes longer, the laminationstructure of the laminated flow laminated at the junction may becomemore likely to be disturbed and the lamination structure having adesired cross-sectional shape may become more difficult to be obtained.

As a technique to improve the lamination accuracy of the layers A and Bat the junction 8 and to allow the range of the shapes applicable inlamination to be broadened, it is also preferable that a flow path (flowpath C) is provided separately for supplying the resins to both walls ofthe second slit section 9 in the thickness direction. FIGS. 6 to 8illustrate an example of an extrusion die having such flow pathdescribed above. FIG. 5 is a plan view of an example of the extrusiondie of the present invention, which die is different from the oneillustrated in FIG. 4. FIG. 7 is a cross-sectional view of an example ofthe extrusion die of the present invention, which die is different fromthe one illustrated in FIG. 6. FIG. 8 is a cross-sectional view of anexample of the inner structure of the extrusion die of the presentinvention taken along the line X-X in FIG. 7. The extrusion dieillustrated in FIGS. 6 to 8 is provided with a junction 12 having theflow path C in place of the junction 8 of the extrusion die illustratedin FIGS. 3 and 5. By providing the flow path C, it becomes possible tocontrol the laminated flow supplied from the nozzles and hole 14 s tothe junction by the flow of the resin supplied from the flow path C, sothat the variety of designable laminated films can be increased. As aresult, it becomes possible to obtain a laminated film having superiorcharacteristics. The resin supplied to the flow path C may be either theresin A or the resin B, or in some cases, may be a resin different fromthe resins A and B. When the resin A or B is used, the flow path may bebranched from the flow path to the hole 14 or the nozzle; however, sincethe resins are preferably supplied to the nozzle and hole 14 from anextrusion machine, an inlet port communicating with the flow path C isprovided on the side wall of the second slit section as illustrated inFIG. 8. In this case, since the flow rate from the flow path C can becontrolled independently from the flow rate from the nozzle and hole 14,the structural control becomes easier. More specifically, the thicknessof the resin to which the resin B is incorporated can be controlled bythe flow rate from the flow path C, and the shape of the layer made ofthe resin B can be controlled by the flow rate from the flow path C.

The flow path C is preferably a slit flow path extending in the widthdirection. When the flow path is a slit flow path extending in the widthdirection, the resins can be supplied without any variation in the flowrate in the width direction and a laminated flow laminated at a highprecision can be obtained. As a result, a laminated film of a large areahaving uniform characteristics can be obtained.

It is also preferable that the distance between the slit flow pathsvaries in the width direction. The distance between slit flow paths usedherein means a length between the walls in the flow direction of theflow path. In this extrusion die, the laminated flow output from thenozzle and hole 14 s is further laminated at the junction to obtain alaminated flow having a number of layers in the width direction.Depending on the flow characteristics of the resin and the flow ratio,there is a difference in the flow rate between the position where thecenter of the nozzle communicates with the junction and the positionbetween the nozzles, resulting, in some cases, in a change in thelamination structure of the laminated flow at the junction. In view ofthis, by narrowing the distance between the slit flow paths at thecenter of the nozzle in the width direction and broadening the spacebetween the flow paths corresponding to the area between the nozzles, itbecomes possible to minimize the change in the flow rate at thejunction, so that a laminated flow laminated at a high precision can beproduced. As a result, a laminated film of a large area having uniformoptical characteristics can be obtained.

FIGS. 9 to 12 illustrate another example of an extrusion die capable offorming the film of the present invention. FIGS. 9 and 10 are a lateralcross-sectional view and a vertical cross-sectional view of theextrusion die, respectively. FIG. 11 is a cross-sectional view takenalong the line A-A in FIGS. 9 and 10.

An extrusion die 21 is provided with a guide port 22 for supplying theresin B and a guide port 23 for supplying the resin A. The guide port 22communicates with a manifold 25 via a flow path 24, and a multi-holeplate 26 having a number of hole 27 s is provided at the downstream sideof the manifold. FIG. 12 is a diagram of the multi-hole plate 26 asviewed from the upstream side. Meanwhile, the guide port 23 communicateswith manifold 29 s via flow path 28 s. The multi-hole plate 26 andmanifold 29 s communicate at a junction 30, from where they areconnected to a lip 31 for extruding the resin to the outside. At thejunction 30, the resin B supplied to the junction 30 via the hole 27 sof the multi-hole late 26 is extruded into the resin A supplied to thejunction 30 via the manifold 29 s. As a result, a composite flow inwhich, within the resin A, dispersions are formed in the shapecorresponding to the shape of the holes can be obtained.

The shape of the holes of the multi-hole plate 26, the number of holes,the distance between the holes and the like are appropriately determineddepending on the desired cross-sectional shape of the resulting resinfilm. The cross-sectional shape of the hole 27 may take various shapessuch as a circle, an ellipsoid, a circular shape, and a polygon such asa triangle, a tetragon, a parallelogram, a pentagon or a hexagon.Particularly, in the extrusion die used for forming the laminated filmof the present invention, the hole 27 is preferably asymmetricalrelative to the center axis in the thickness direction. The center axisin the thickness direction used herein refers to a straight lineparallel to the width direction and at an equal distance from the apexesof the upper and lower surfaces of each hole in the width direction. Byusing such a hole, it becomes possible to obtain a laminated film havingthe layer B asymmetrical relative to the center axis in the thicknessdirection. Further, a shape such as a rectangle having a very long sidecan also be formed by allowing the resin Bs to join at the junction byarranging circular or rectangular holes side by side. When using suchextrusion die, the number of the layer Bs can be adjusted with thenumber of holes. The number of holes is 10 or larger, preferably 250 orlarger, more preferably 500 or larger, and most preferably 1,000 orlarger. Further, the cross-sectional width of the layer B can beadjusted with the shape of the nozzles and extruded amount therefrom.

The laminated flow thus formed in the extrusion die is extruded from theextrusion die, and subsequently cooled and solidified by a casting drum,a calendar ring roll or the like. Since the distance between the layerBs may vary due to a neck-down phenomenon when the laminated flow isextruded from the extrusion die, it is preferable to provide an edgeguide at the end of the extrusion die lip. The edge guide is providedbetween the extrusion die lip and cooling member in order to restrictthe end of a resin film extruded from the extrusion die. The neck-downcan be suppressed by a surface tension provided by a slight contactbetween the edge guide and the resin. In this manner, although thelaminated film extruded from the extrusion die is thinned in thethickness direction in accordance with the relation between the extrudedamount and the extrusion velocity, since the dimension in the widthdirection will not be changed, the precision of each layer in the widthdirection is improved.

For cooling and solidifying the laminated flow, it is preferable to usea method of tightly adhering the laminated flow to a cooling member suchas a casting drum by an electrostatic force using an electrode of awire-, tape-, needle-, knife-shape or the like, a method of tightlyadhering the laminated flow to a cooling member such as a casting drumby blowing air from an apparatus of a slit-, spot-, plane-shape or thelike, or a method of tightly adhering the laminated flow by using aroll.

The thus obtained laminated film is subjected to stretching or the likeif necessary, and wound by a winder. The laminated film of the presentinvention is preferably a film not stretched or a uniaxially stretchedfilm. More preferably, the laminated film of the present invention is afilm not stretched and almost completely maintains the shape of thelaminated flow laminated at a high precision by the extrusion die; sothat a width-direction multi-layered laminated film of a large areahaving uniform characteristics can be obtained.

The laminated film of the present invention is preferably wound withoutoscillation. If oscillation is performed, it is not preferable because afilm roll of the layer B may move in a zigzag way. However, there is aproblem that, if oscillation is not performed, the wound appearance ofthe film roll is degraded due to the uneven thickness of the film,resulting in the formation of a film having poor flatness. In view ofthis, when winding the laminated film of the present invention, it ispreferable to perform a knurling process. It is also preferable tolaminate a protective film.

Description will be made below on the differences between the extrusiondie according to embodiments of the present invention and a knownextrusion die.

In the method of laminating a film in the width direction by using amixer, which method is disclosed in Patent Documents 1 and 2, severallayers of laminated flow are divided and re-laminated to increase thenumber of layers. However, since the lamination structure changes due toa change in the flow velocity and the flow direction during the processof the division and re-lamination, variation in the distance between thelayers, the cross-sectional area and the shape of each layer becomessevere.

In the method disclosed in Patent Document 3 using an integratedapparatus having a number of slits, it is possible to laminate a desirednumber of layers in a uniform shape by using the slits and achieve anconsiderable improvement in the lamination precision, compared to amethod of laminating layers in the width direction by using a mixer.However, this method also has a limit.

As for the slit, it is advantageous that the space between slits and thewidth of the partition wall between slits be wide so some degree becauseof the problems in the strength and the processing precision of eachslit. It is therefore advantageous to compress a flow after laminationto a desired width. Because of this, a slight variation occurs in thelayer shape at various positions in the width direction during thecompression process of the flow path in the width direction.Consequently, the lamination precision is insufficient particularly foruse having a major influence on the characteristics associated with theshape of the laminated layer, such as optical diffusion and collection.Further, in addition to the influence of the compression in the widthdirection, due to the long flow length between the slit where thelaminated flow is produced and the extrusion die from which thelaminated flow is extruded, there are cases where the shape laminatedvia the slits is deformed during the resin flow. In order to increasethe number of the layers, since the apparatus has to be enlarged, theassembly and handling performance becomes inferior, so that such anapparatus is not suitable for laminating a very large number of layers.In the extrusion die of the present invention, by making the nozzles andholes small in size, the nozzles and holes can be arranged more denselythan the slits. Since the flow path is not required to be compressed inthe width direction after lamination and it is possible even to shortenthe flow length in order to carry out lamination within the extrusiondie, a high lamination precision can be attained. Further, by denselyarranging the nozzles and holes and by having an integrated extrusiondie, the apparatus can be made compact; therefore, such apparatus havingexcellent handling performance is advantageous in laminating a number oflayers.

In an integrated apparatus having a number of slits, processingsrequiring time and skills such as wire discharge processing areperformed because slit processing is required with a high precision,resulting in a high manufacturing cost. Since increasing the number oflayers has considerable influence on the manufacturing cost, it isdifficult to simultaneously attain broadening of the film width and anincrease in the number of layers. In contrast, in the extrusion dieaccording to an embodiment of the present invention, since the nozzlesnecessary for manufacturing the extrusion die can be easily prepared bycutting pipes having the same diameter, the extrusion die capable oflaminating layers at a high precision can be manufactured at a low cost;therefore, this is advantageous in increasing the number of layers andbroadening the film. In addition, since the diameters of the nozzles canbe made approximately uniform by cutting pipes having the same diameter,the flow rate of the layer B in the width direction can be uniformized,so that a high lamination precision can be easily attained. In thismanner, as compared to the conventional techniques, it is possible toobtain a laminated film having a broader width by using the extrusiondie of the present invention.

In an integrated apparatus having a number of slits, only a rectangularcross-sectional shape can be produced because of its lamination method.On the other hand, in the extrusion die according to an embodiment ofthe present invention, it is possible to form a variety of layer Bcross-sectional shapes because of the shapes of the nozzles, holes andholes, so that a laminated film having superior characteristics can beobtained. Also in an integrated apparatus having a number of slits,since all layers flow within the apparatus in contact with the walls ofthe apparatus, there is a problem that the shape of each layer is likelyto be changed due to the difference among the viscosities and among theflow rates of the laminated resins. On the other hand, the resin Bssupplied from the nozzles are always covered with the resin A suppliedfrom the holes 14 or the resin supplied from the flow path C; therefore,the resin Bs flow keeping a distance from the wall surfaces.Consequently, a change in the shape of the layer during the flow can besuppressed, so that it is possible to obtain a laminated film having ahigher lamination precision.

EXAMPLES

Evaluation methods of the physical properties used in the presentinvention will now be described.

(1) Cross-Sectional Width, Average Cross-Sectional Width, Number ofLayers, and Shape of Layer B

First, a film width direction-thickness direction cross-section to beobserved was smoothened with a polishing machine. The cross-section ofthe film was cut out using a utility knife. The film was sandwiched onboth the surface by acrylic plates 2 mm thick and fixed to a jig. Next,the cross-section of the film was smoothened using a polishing machine(NAP-240 from NISSHIN KASEI CO., LTD.) by adhering a #6000 gritpolishing film (abrasive, aluminum oxide) to a polishing plate andpolishing the film at 240 rpm of the polishing plate for 10 minutesusing pure water as a polishing solution. This process was carried outsequentially for every width of the films. The layer B was then measuredfor cross-sectional width, number of layers, and shape using anoncontact three coordinate measuring machine (NEXIV VMR-H3030TZ fromNikon Corporation).

Samples were placed at the center of the stage of the noncontact threecoordinate measuring machine such that the smoothened cross-sectioncould be seen, and were photographed at 3 magnification in cases wherethe cross-sectional width of the layer B was about 800 μm, at 10magnification in cases where the cross-sectional width of the layer Bwas about 100 μm, and at 100 magnification in cases where thecross-sectional width of the layer B was about 10 μm. The shape of thelayer B was determined from the images obtained. When the photographingwas not completed within one stroke range, the measurement was continuedafter shifting and resetting the samples. The captured images wereanalyzed with an image processing software, Image-Pro Plus ver. 4 (soldby Planetron Co., Ltd.), and image processing was carried out asrequired. The image processing was carried out for clarifying the shapeof the layers; for example, binarization by the software attached to theproduct, low-pass filter processing and the like were carried out. Animage analysis program was used for the analysis and the layer B wasmeasured, for every width of the films, for cross-sectional width,center of gravity, cross-sectional area, and coordinate information.

With respect to the cross-sectional width obtained, the averagecross-sectional width was defined as the mean value of all thecross-sectional width; as an accuracy of the cross-sectional width, thefilm in which the number of layer Bs which satisfied the averagecross-sectional width ±10 μm was more than half was defined as B, thefilm in which the layer B which satisfied the average cross-sectionalwidth ±10 μm existed continuously in the width direction for 300 mm ormore was defined as A, the film in which the number of layer Bs whichsatisfied the average cross-sectional width ±10 μm was less than halfwas defined as C, and the film in which the cross-sectional width of thelayer B varied periodically was further defined as D. For all adjacentlayer Bs, the distance between them was calculated from the center ofgravity obtained, the film in which the layer B, wherein the distancebetween adjacent layer Bs, P, was 0.90 times to 1.10 times as large asthe distance between adjacent layer Bs at the center of the film in thewidth direction, Pc, existed continuously in the width direction for 300mm or more, and for less than 300 mm, were defined as A and C,respectively. The film in which the distance between adjacent layer Bsvaried periodically was further defined as D. With respect to thecross-sectional area, the film in which the layer B, wherein thecross-sectional area of the layer B, A, was 0.90 times to 1.10 times aslarge as the cross-sectional area of the layer B located at the centerof the film in the width direction, Ac, existed for 300 mm or more, andfor less than 300 mm, were defined as A and C, respectively. For eachlayer B, a centerline, which passed through the midpoint of thecoordinates at both ends in the thickness direction and was parallelwith the surface of the film, was constructed and the cross-sectionalarea divided by the centerline was detected. S1/S2 was calculated fromS1 and S2 for each layer, and a layer whose mean value of S1/S2 was notmore than 0.8 was defined as A and a layer whose mean value of S1/S2 wasmore than 0.8 was defined as C (see Table).

(2) Transmittance Ununiformity

All light transmittances were measured on the basis of JIS K7736-1(1996) using NIPPON DENSHOKU INDUSTRIES CO., LTD. Turbidimeter NDHS5000.For every width of the films, the all light transmittances were measuredat 10 points at regular intervals and the difference between the maximumand minimum values of the all light transmittances at the 10 points wasdefined as transmittance ununiformity.

(3) Average Loss, Loss Ununiformity

The measurements were made by the cut back method (IEC60793-C1A) inaccordance with JIS C6823 (1999) at 25° C., 65% RH. Samples with testinglength of 10 cm, 9 cm, 8 cm and 7 cm were provided and each sample wasmeasured for insertion loss. As the light source, an LED (0901Amanufactured by Anritsu Corporation) with a wavelength of 850 nm wasused, and light was input into the sample through a mode scrambler. Asthe optical fibers, a multimode fiber type GI (NA0.21) having a diameterof 50 μm was used for the input side, and an SI type fiber (NA0.22)having a core diameter of 0.2 mm was used for the detection side. In theinput/output of the light, optical axes were aligned with a waveguidealignment device. As the detector, an optical power sensor (MA9421A,Anritsu Corporation) was used. Propagation loss was determined using theleast-squares method by plotting the insertion loss for the length. Thatis, the inclination of a linear expression obtained was defined as loss.In the least square, only the contribution ratio R2 of 0.99 or more wasadopted as the propagation loss. If the contribution ratio was not morethan 0.99, remeasurements such as realignment and readjustment of thesamples were repeated until the value of 0.99 or more was obtained. Forevery width of the films, each loss at the 10 points at regularintervals was measured, and the mean value was defined as average loss.The difference between the maximum and minimum values of the losses atthe 10 points was defined as loss ununiformity.

(4) Winding Hardness Variation

The surface layer of the film roll of a winding length of 500 m wasmeasured for winding hardness at 10 points in the width direction usingKOBUNSHI KEIKI CO., LTD. ASKER A type rubber hardness tester inaccordance with JIS K7215 (1986). The difference between the maximum andminimum values was defined as winding hardness variation.

Example 1

The following resin A and resin B were provided.

Resin A: Polypropylene (PP)

Polypropylene Noblen WF836DG manufactured by Sumitomo Chemical

Resin B: Polycarbonate (PC)

Polycarbonate LC1700 manufactured by Idemitsu Kosan

Then resin A was fed to an extruder 1 and resin B was fed to an extruder2. The resins were melted in the respective extruders at 280° C., andwere flown into an extrusion die 700 mm wide as shown in FIGS. 3 to 5after passing through a gear pump and a filter. The extrusion die wasprovided with 600 rectangular nozzles, through which the resin B flew.The sheet from the extrusion die was nip-cast on a drum maintained at atemperature of 80° C. while being engaged at the end portions thereofwith edge guides. The resultant was then cut off by 45 mm at both endportions and wound with a winder without causing an oscillation. Next,the resultant was wound with a slitter while being subjected to aknurling-process and laminated with a protective film (PANACCorporation, heat-resistant protective film HP25) on one side to providea film roll. The laminated film obtained had a thickness of 1000 μm(excluding the protective film). Resin B was arranged successively inthe longitudinal direction and at substantially regular intervals of 1mm±0.05 mm in the width direction, forming the structure in which theresin B was covered with resin A. The cross-sectional shape of the resinB was substantially circular and there were 600 pieces of the resin Bwith a cross-sectional width of 800 μm±8 μm. Table 1 shows the structureand performance of the laminated film obtained. The film obtained wasable to transmit light with a small loss and therefore suitable for anoptical waveguide, light guide and illumination apparatus. On the otherhand, although the film had a capability of emitting the light that hadimpinged, though it was low, on the film perpendicularly to the surfacein the oblique direction to the film surface, this film could be used asa light-collecting film or an anisotropic diffusion film.

Example 2

A film was prepared under substantially the same conditions as inExample 1 except that the extrusion die used was 1900 mm wide andprovided with 1800 nozzles and that the discharge rate was adjusted. Thefilm obtained had a thickness of 1000 μm (excluding the protectivefilm). Resin B was arranged successively in the longitudinal directionand at substantially regular intervals of 1 mm±0.09 mm in the widthdirection, forming the structure in which the resin B was covered withresin A. The cross-sectional shape of the resin B was substantiallycircular and there were 1800 pieces of the resin B with across-sectional width of 800 μm±9 μm. Table 1 shows the structure andperformance of the laminated film obtained. The film obtained was ableto transmit light with a small loss and therefore suitable for anoptical waveguide, a light guide and an illumination apparatus.

Example 3

The following resin A and resin B were provided.

Resin A: Polycarbonate (PC)

Polycarbonate LC1700 manufactured by Idemitsu Kosan

Resin B: Polycarbonate (PC)+carbon black (CB) 2 wt %

Then resin A was fed to an extruder 1 and resin B was fed to an extruder2. The resins were melted in the respective extruders at 290° C., andwere flown into an extrusion die 700 mm wide as shown in FIGS. 3 to 5after passing through a gear pump and a filter. The extrusion die wasprovided with 3000 rectangular nozzles that were longer in the thicknessdirection than in Example 1, through which the resin B flew. The sheetfrom the extrusion die was nip-cast on a drum maintained at atemperature of 80° C. while being engaged at the end portions thereofwith edge guides. The resultant was then cut off by 45 mm at both endportions and wound with a winder without causing an oscillation. Next,the resultant was wound with a slitter while being subjected to aknurling-process and laminated with a protective film (PANACCorporation, heat-resistant protective film HP25) on one side to providea film roll. The film obtained had a thickness of 500 μm (excluding theprotective film). Resin B was arranged successively in the longitudinaldirection and at substantially regular intervals of 200 μm±10 μm in thewidth direction, forming the structure in which the resin B was coveredwith resin A. The cross-sectional shape of the resin B was substantiallyrectangular and there were 3000 pieces of resin B with a height (lengthin the thickness direction) of about 450 μm and a cross-sectional widthof 100 μm±2 μm. Table 1 shows the structure and performance of thelaminated film obtained. The film obtained substantially transmitted thelight in the direction perpendicular to the film surface but hardlytransmitted the light that was oblique by 15° or more in the widthdirection to the film surface. This film was suitable as a view anglecontrol film.

Example 4

The following resin A and resin B were provided.

Resin A: Polyethylene naphthalate (PEN)

P100 manufactured by invista

Resin B: Polyester copolymer (PCT/I)

Z6006 manufactured by Eastman

Then resin A was fed to an extruder 1 and resin B was fed to an extruder2. The resins were melted in the respective extruders at 290° C., andwere flown into an extrusion die 700 mm wide as shown in FIGS. 3 to 5after passing through a gear pump and a filter. The extrusion die wasprovided with 3000 rectangular nozzles that were oblique by 45° to thesecond slit surface, through which the resin B flew. The sheet from theextrusion die was closely contacted with a drum maintained at atemperature of 40° C. by applying high voltages to a wire electrodewhile being engaged at the end portions thereof with edge guides. Theresultant was then cut off by 45 mm at both end portions and wound witha winder without causing an oscillation. Next, the resultant was woundwith a slitter while being subjected to a knurling-process and laminatedwith a protective film (PANAC Corporation, heat-resistant protectivefilm HP25) on one side to provide a film roll. The film obtained had athickness of 500 μm (excluding the protective film). Resin B wasarranged successively in the longitudinal direction and at substantiallyregular intervals of 200 μm±15 μm in the width direction, forming thestructure in which the resin B was covered with resin A. Thecross-sectional shape of the resin B was substantially parallelogram andthere were 3000 pieces of resin B with a height (length in the thicknessdirection) of about 450 μm and a cross-sectional width of 100 μm±2 μm.Table 1 shows the structure and performance of the laminated filmobtained. The film obtained had a capability of emitting the light thathad impinged on the film perpendicularly to the surface in the obliquedirection to the film surface. This film was suitable as alight-collecting film or an anisotropic diffusion film.

Example 5

The following resin A and resin B were provided.

Resin A: Polycarbonate (PC)

Polycarbonate LC1700 manufactured by Idemitsu Kosan

Resin B: Polycarbonate (PC)+Polymethylpentene (PMP) 25 wt %

DX820 manufactured by Mitsui Chemicals

Then resin A was fed to an extruder 1 and resin B was fed to an extruder2. The resins were melted in the respective extruders at 280° C., andwere flown into an extrusion die 700 mm wide as shown in FIGS. 3 to 5after passing through a gear pump and a filter. The extrusion die wasprovided with 3000 rectangular nozzles that were longer in the thicknessdirection than in Example 1, through which the resin B flew. The sheetfrom the extrusion die was nip-cast on a drum maintained at atemperature of 80° C. while being engaged at the end portions thereofwith edge guides. The resultant was then cut off by 45 mm at both endportions and wound with a winder without causing an oscillation. Next,the resultant was wound with a slitter while being subjected to aknurling-process and laminated with a protective film (PANACCorporation, heat-resistant protective film HP25) on one side to providea film roll. The film obtained had a thickness of 500 μm (excluding theprotective film). Resin B was arranged successively in the longitudinaldirection and at substantially regular intervals of 200 μm±10 μm in thewidth direction, forming the structure in which the resin B was coveredwith resin A. The cross-sectional shape of the resin B was substantiallyrectangular and there were 3000 pieces of resin B with a height (lengthin the thickness direction) of about 450 μm and a cross-sectional widthof 100 μm±2 μm. Table 1 shows the structure and performance of thelaminated film obtained. The film obtained strongly diffused the light,only in longitudinal direction, that had impinged on the film in thedirection perpendicular to the surface. This film was suitable as ananisotropic diffusion film.

Example 6

The following resin A and resin B were provided.

Resin A: Polymethylmethacrylate (PMMA)

MGSS manufactured by Sumitomo Chemical

Resin B: Polystyrene (PS)

G120K manufactured by Japan PolyStyrene Inc.

Then resin A was fed to an extruder 1 and resin B was fed to an extruder2. The resins were melted in the respective extruders at 230° C., andwere flown into an extrusion die 700 mm wide as shown in FIGS. 3 to 5after passing through a gear pump and a filter. The extrusion die wasprovided with 600 rectangular nozzles, through which the resin B flew.The sheet from the extrusion die was nip-cast on a drum maintained at atemperature of 80° C. while being engaged at the end portions thereofwith edge guides. The resultant was then cut off by 45 mm at both endportions and wound with a winder without causing an oscillation. Next,the resultant was wound with a slitter while being subjected to aknurling-process and laminated with a protective film (PANACCorporation, heat-resistant protective film HP25) on one side to providea film roll. The laminated film obtained had a thickness of 1000 μm(excluding the protective film). Resin B was arranged successively inthe longitudinal direction and at substantially regular intervals of 1mm±0.10 in the width direction, forming the structure in which the resinB was covered with resin A. The cross-sectional shape of the resin B wassubstantially circular and there were 600 pieces of resin B with across-sectional width of 800 μm±8 μm. Table 1 shows the structure andperformance of the laminated film obtained. The film obtained was ableto transmit light with a small loss and therefore suitable for anoptical waveguide, a light guide and an illumination apparatus.

The end face of the film obtained in the width direction was immersed inacetic acid at 50° C. for one day and the covering PMMA was dissolved toobtain a laminated film, the end portions of which were made up of anumber of polystyrene yarn. Bundling the polystyrene yarn of thislaminated film allowed for easy individual connection to the pointsource of LED.

Example 7

A laminated film was obtained in substantially the same manner as inExample 1 except that the film roll was obtained with a slitter withoutbeing subjected to a knurling-process and laminated with a protectivefilm. The laminated film obtained had a thickness of 1000 μm (excludingthe protective film). Resin B was arranged successively in thelongitudinal direction and at intervals of 1 mm±0.2 mm in the widthdirection; the layer Bs whose distance to the adjacent layer Bs was 0.90times to 1.10 times as large as the distance between the adjacent layerBs at the center in the width direction existed continuously for 0.05 mmat most. The structure was formed in which the resin B was covered withresin A. The cross-sectional shape of the resin B was substantiallycircular and there were 600 pieces of resin B with a cross-sectionalwidth of 800 μm±8 μm. Table 1 shows the structure and performance of thelaminated film obtained. The film obtained, though it had slightly poorflatness, was able to transmit light with a small loss and thereforesuitable for an optical waveguide, a light guide and an illuminationapparatus.

Example 8

A film was prepared under substantially the same conditions as inExample 1 except that the die shape, such as die width and number ofnozzles, and the discharge rate were changed. The laminated filmobtained had a thickness of 1650 μm (excluding the protective film) anda width of 600 mm. Resin B was arranged successively in the longitudinaldirection and at substantially regular intervals of 1.8 mm ±0.1 mm inthe width direction, forming the structure in which the resin B wascovered with resin A. The cross-sectional shape of the resin B wassubstantially circular and there were 500 pieces of resin B with across-sectional width of 1600 μm±9 μm. Table 1 shows the structure andperformance of the laminated film obtained. The film obtained was ableto transmit light with a small loss and therefore suitable for anoptical waveguide, a light guide and an illumination apparatus.

Example 9

A film was prepared under substantially the same conditions as inExample 3 except that the ratio of the discharge rate of the resin waschanged.

The film obtained had a thickness of 500 μm (excluding the protectivefilm) and a width of 600 mm. Resin B was arranged successively in thelongitudinal direction and at substantially regular intervals of 200μm±20 μm in the width direction, forming the structure in which theresin B was covered with resin A. The cross-sectional shape of the resinB was substantially rectangular and there were 3000 pieces of resin Bwith a height (length in the thickness direction) of about 450 μm and across-sectional width of 9 μm±0.1 μm. Table 1 shows the structure andperformance of the laminated film obtained. The film obtainedsubstantially transmitted the light in the direction perpendicular tothe film surface but hardly transmitted the light that was oblique by45° or more in the width direction to the film surface. This film wassuitable as a view angle control film.

Example 10

A film was prepared under substantially the same conditions as inExample 1 except that the extrusion die having the passage C as shown inFIGS. 6 to 8 was used, where resin A was supplied to the passage C andthe supply flow rate was adjusted such that the total flow rate of theresin A supplied from the hole 14 and the resin A from the passage C wasthe same as in Example 1. The laminated film obtained had a thickness of1000 μm (excluding the protective film). Resin B was arrangedsuccessively in the longitudinal direction and at regular intervals of 1mm±0.03 mm in the width direction, forming the structure in which theresin B was covered with resin A. The cross-sectional shape of the resinB was substantially circular and there were 600 pieces of resin B with across-sectional width of 800 μm±3 μm. Table 1 shows the structure andperformance of the laminated film obtained. The film obtained, having ashape close to true circle compared to the film shown in Example 1, wasable to transmit light with a small loss, and more suitable for anoptical waveguide, a light guide and an illumination apparatusparticularly than the film shown in Example 1 because the connectionwhen used was easy.

Example 11

A film was prepared under the same conditions as in Example 8 exceptthat the rectangular nozzles that were longer in the thickness directionthan in Example 1 were used. The laminated film obtained had a thicknessof 500 μm (excluding the protective film) and a width of 600 mm. Resin Bwas arranged successively in the longitudinal direction and atsubstantially regular intervals of 1.8 mm±0.1 mm in the width direction,forming the structure in which the resin B was covered with resin A. Thecross-sectional shape of the resin B was substantially rectangular andthere were 500 pieces of resin B with a height (length in the thicknessdirection) of about 450 μm and a cross-sectional width of 1600 μm±9 μm.Table 1 shows the structure and performance of the laminated filmobtained. The film obtained was further subjected to surface rougheningby applying an embossing process thereto using an embossing roll havinga 100 μm pitch and 100 μm deep groove in the width direction. The filmobtained had a part not covered by resin A and emitted light from theroughened surface prepared by the embossing process when the lightimpinged on the end faces of the film; it was suitable as planeillumination.

Example 12

A film was prepared and an embossing process was carried out under thesame conditions as in Example 14 except that the extrusion die having awidth of 1000 mm was used. The laminated film obtained had a thicknessof 500 μm (excluding the protective film) and a width of 900 mm. Resin Bwas arranged successively in the longitudinal direction and atsubstantially regular intervals of 2.8 mm±0.1 mm in the width direction,forming the structure in which the resin B was covered with resin A. Thecross-sectional shape of the resin B was substantially rectangular andthere were 500 pieces of resin B with a height (length in the thicknessdirection) of about 450 μm and a cross-sectional width of 2700 μm±14 μm,about 70% of the layer Bs satisfying the average cross-sectional width±10 μm. Table 1 shows the structure and performance of the laminatedfilm obtained. The film obtained had a part not covered by resin A andemitted light from the roughened surface prepared by the embossingprocess when the light impinged on the end faces of the film; it wassuitable as plane illumination but had slightly low brightness comparedto Example 14.

Example 13

A film was prepared under the same conditions as in Example 5 exceptthat the extrusion die was used, comprising nozzles which were providedsuch that the distance between the cross-sectional width of the layer Band the adjacent layer B periodically varied at 25 mm intervals. Thefilm obtained had a thickness of 500 μm (excluding the protective film).Resin B was arranged successively in the longitudinal direction and thedistance varied in the range of 150 to 250 μm at 25 mm intervals in thewidth direction, forming the structure in which the resin B was coveredwith resin A. The cross-sectional shape of the resin B was substantiallyrectangular and there were 3000 pieces of resin B with a height (lengthin the thickness direction) of about 450 μm and a cross-sectional widthvarying in the range of 75 to 125 μm at 25 mm intervals. Table 1 showsthe structure and performance of the laminated film obtained. The filmobtained strongly diffused the light, only in longitudinal direction,that had impinged on the film in the direction perpendicular to thesurface; the film effectively prevented the brightness uniformity of thelamps especially when mounted on a display on which lamps were arrangedat 25 mm intervals.

Example 14

A film was prepared under the same conditions as in Example 9 exceptthat the resins below were used and the ratio of the discharge rate ofthe resin was changed.

Resin A: Polycarbonate (PC)

Polycarbonate LC1700 manufactured by Idemitsu Kosan

Resin B: Polycarbonate (PC)+Polymethylpentene (PMP) 25 wt %

DX820 manufactured by Mitsui Chemicals

The film obtained had a thickness of 500 μm (excluding the protectivefilm) and a width of 600 mm. Resin B was arranged successively in thelongitudinal direction and at substantially regular intervals of 200μm±18 μm in the width direction, forming the structure in which theresin B was covered with resin A. The cross-sectional shape of the resinB was substantially rectangular and there were 3000 pieces of resin Bwith a height (length in the thickness direction) of about 450 μm and across-sectional width of 20 μm±1 μm. Table 1 shows the structure andperformance of the laminated film obtained. The film obtained stronglydiffused the light, only in the longitudinal direction, that hadimpinged on the film in the direction perpendicular to the surface, butslight optical ununiformity was observed. This film was suitable as ananisotropic diffusion film.

Example 15

A film was prepared under the same conditions as in Example 1 exceptthat the ratio of the discharge rate of the resin and the speed of thecasting drum were changed. The laminated film obtained had a thicknessof 200 μm (excluding the protective film). Resin B was arrangedsuccessively in the longitudinal direction and at substantially regularintervals of 1 mm±0.05 mm in the width direction, forming the structurein which the resin B was covered with resin A. The cross-sectional shapeof the resin B was substantially circular and there were 600 pieces ofresin B with a cross-sectional width of 100 μm±12 μm. However, thevariability in cross-sectional area was pronounced in some parts. Table1 shows the structure and performance of the laminated film obtained.The film obtained was able to transmit light with a small loss andtherefore suitable especially for communication uses.

Example 16

The following resin A and resin B were provided.

Resin A: Polyethylene terephthalate (PET)+Polymethylpentene (PMP) 1 wt %

Resin B: Polyethylene terephthalate (PET)+Polymethylpentene (PMP) 40 wt%

The above-described resins were polymerized by the method describedbelow. First, to the mixture of 100 parts by weight of dimethylterephthalate and 60 parts by weight of ethylene glycol, calcium acetatewas added as an ester exchange reaction catalyst. The ester exchangereaction was performed by heating the resulting mixture to distill offmethanol. Next, antimony trioxide as a polymerization catalyst andphosphoric acid as a heat stabilizer were added to the ester exchangereaction products, and the mixture was transferred to a polycondensationreaction vessel. Then, pressure in the reaction system was graduallyreduced with heating. The reactant was stirred inside at a temperatureof 290° C. under reduced pressure and polymerized while distilling offmethanol to obtain PET resin.

Then resin A was fed to an extruder 1 and resin B was fed to an extruder2. The resins were melted in the respective extruders at 280° C., andwere flown into an extrusion die 500 mm wide as shown in FIGS. 9 to 12after passing through a gear pump and a filter. The extrusion die wasprovided with 13 semicircular pores, through which the resin B flew. Thesheet from the extrusion die was quickly solidified on a drum maintainedat a temperature of 25° C. by application of an electrostatic voltagewhile being engaged at the end portions thereof with edge guides. Theresultant was then cut off by 45 mm at both end portions and wound witha winder without causing an oscillation. The laminated film obtained hada thickness of 1500 μm. Resin B was arranged successively in thelongitudinal direction and at substantially regular intervals of 25000μm±1000 μm in the width direction, forming the structure in which theresin B was covered with resin A. The cross-sectional shape of the resinB was substantially semicircular and there were 13 pieces of resin Bwith a cross-sectional width of 10000 μm±500 μm and a thickness of 500μm±20 μm. The particle size of PMP dispersed in the resin A and theresin B was 10 μm. Table 1 shows the structure and performance of thelaminated film obtained. The film obtained was able to diffuse the lightstrongly at the layers made up of resin B (layer Bs) and to prevent thebrightness uniformity of the lamps by arranging the layer Bs above the25 mm-interval lamps of a back light.

Example 17

A film was prepared under the same conditions as in Example 16 exceptthat the resins below were used.

Resin A: Polyethylene terephthalate (PET)+Polymethylpentene (PMP) 1 wt %

Resin B: Polyethylene terephthalate (PET)+titanium oxide particle (Ti) 4wt %

The laminated film obtained had a thickness of 1500 μm. Resin B wasarranged successively in the longitudinal direction and at substantiallyregular intervals of 25000 μm±1000 μm in the width direction, formingthe structure in which the resin B was covered with resin A. Thecross-sectional shape of the resin B was substantially semicircular andthere were 13 pieces of resin B with a cross-sectional width of 10000μm±500 μm and a thickness of 500 μm±20 μm. The particle size of PMPdispersed in the resin A was 10 μm and the particle size of Ti particlesdispersed in the resin B was 0.25 μm. Table 1 shows the structure andperformance of the laminated film obtained. The film obtained was ableto diffuse the light strongly at the layers made up of resin B (layerBs) and to prevent the brightness uniformity of the lamps moreeffectively by arranging the layer Bs above the 25 mm-interval lamps ofa back light.

Example 18

The following resin A and resin B were provided.

Resin A: Polyethylene terephthalate (PET)+Polymethylpentene (PMP) 1 wt %

Resin B: Polyester copolymer (PCT/1)+Polymethylpentene (PMP) 40 wt %

The extrusion die comprising 1200 semicircular pores was used. A filmwas prepared under the same conditions as in Example 16 except thatthese resins and extrusion die were used. The film obtained had athickness of 250 μm. Resin B was arranged successively in thelongitudinal direction and at substantially regular intervals of 300μm±10 μm in the width direction, forming the structure in which theresin B was covered with resin A. The cross-sectional shape of the resinB was pseudo-semicircular and there were 1200 pieces of resin B with across-sectional width of 200 μm±7 μm and a thickness of 120 μm±2 μm. Theparticle size of PMP dispersed in the resin A and the resin B was 10 μm.Table 1 shows the structure and performance of the laminated filmobtained. The film obtained had a strong anisotropic diffusibility andwas able to prevent the brightness uniformity of the back light lamps.

Comparative Example 1

The following resin A and resin B were provided.

Resin A: Polypropylene (PP)

Polypropylene Noblen WF836DG manufactured by Sumitomo Chemical

Resin B: Polycarbonate (PC)

Polycarbonate LC1700 manufactured by Idemitsu Kosan

Then resin A was fed to an extruder 1 and resin B was fed to an extruder2. The resins were melted in the respective extruders at 280° C. andpassed through a gear pump and a filter. Then the resin A and the resinB were laminated alternately in the width direction into 1200 layers intotal with known square mixer and extruded in the form of a sheet fromthe extrusion die 700 mm wide. The sheet from the extrusion die wasnip-cast on a drum maintained at a temperature of 80° C. while beingengaged at the end portions thereof with edge guides. The resultant wasthen cut off by 45 mm at both end portions and wound with a winderwithout causing an oscillation. Next, the resultant was wound with aslitter while being subjected to a knurling-process and laminated with aprotective film (PANAC Corporation, heat-resistant protective film HP25)on one side to provide a film roll. The laminated film obtained had athickness of 1000 μm (excluding the protective film). However, althoughthe resin B was arranged successively in the longitudinal direction, itwas not arranged at regular intervals in the width direction. Further,the shape of the layers was disturbed such that almost all the layerscombined to the adjacent layers. Hence, the number of layer Bs having across-sectional width of not less than 0.1 μm and not more than 10000 μmwas below 300. Table 1 shows the structure and performance of thelaminated film obtained. The film obtained could hardly transmit thelight.

TABLE 1 Example Example Example Example 1 2 3 4 Resin A Resin PP PP PCPEN Additive — — — — Refractive Index 1.48 1.48 1.59 1.64 Resin B ResinPC PC PC PCT/I Additive — — CB — Refractive Index 1.59 1.59 1.59 1.56Difference Between Refractive Indices 0.11 0.11 0.00 0.08 B LayerAverage Cross- 800 800 100 100 Sectional Width (μm) Accuracy of Cross- AA A A Sectional Width Accuracy of Interval A A A A Accuracy of Cross- AA A A Sectional Area S1/S2 C C C C Number of Layers 600 1800 3000 3000Shape of Cross- Circle Circle Rectangle Parallelogram SectionCovered/Uncovered Covered Covered Covered Covered Film Width (mm) 6001800 600 600 Film (μm) 1000 1000 500 500 Thickness Transparency (%) — —1 0.5 Ununiformity Average Loss (dB) 0.1 0.1 — — Loss (dB) 0.02 0.02 — —Ununiformity Winding — 3 6 2 2 Hardness Variation Example ExampleExample Example 5 6 7 8 Resin A Resin PC PMMA PP PP Additive — — — —Refractive Index 1.59 1.49 1.48 1.48 Resin B Resin PC PS PC PC AdditivePMP — — — Refractive Index — 1.59 1.59 1.59 Difference BetweenRefractive Indices — 0.10 0.11 0.11 B Layer Average Cross- 100 800 8001600 Sectional Width (μm) Accuracy of Cross- A A A A Sectional WidthAccuracy of Interval A A C A Accuracy of Cross- A A A A Sectional AreaS1/S2 C C C C Number of Layers 3000 600 600 500 Shape of Cross-Rectangle Circle Circle Circle Section Covered/Uncovered Covered CoveredCovered Covered Film Width (mm) 600 600 600 600 Film 500 1000 1000 1650Thickness (μm) Transparency 2 — — — Ununiformity (%) Average Loss (dB) —0.05 0.1 0.12 Loss (dB) — 0.01 0.02 0.03 Ununiformity Winding — 2 3 11 3Hardness Variation Example Example Example Example 9 10 11 12 Resin AResin PC PP PP PP Additive — — — — Refractive Index 1.59 1.48 1.48 1.48Resin B Resin PC PC PC PC Additive CB — — — Refractive Index 1.59 1.591.59 1.59 Difference Between Refractive Indices 0.00 0.11 0.11 0.11 BLayer Average Cross- 9 800 1600 2700 Sectional Width (μm) Accuracy ofCross- A A A B Sectional Width Accuracy of Interval A A A A Accuracy ofCross- A A A A Sectional Area S1/S2 C C C C Number of Layers 3000 600500 500 Shape of Cross- Rectangle Circle Rectangle Circle SectionCovered/Uncovered Covered Covered Covered Covered Film Width (mm) 600600 600 900 Film (μm) 450 1000 1650 1650 Thickness Transparency (%) 1 —— — Ununiformity Average Loss (dB) — 0.07 — — Loss (dB) — 0.01 — —Ununiformity Winding — 2 3 5 6 Hardness Variation Example ExampleExample Example 13 14 15 16 Resin A Resin PC PC PP PET Additive — — —PMP Refractive Index 1.59 1.59 1.48 1.59 Resin B Resin PC PC PC PETAdditive PMP PMP — PMP Refractive Index — — 1.59 1.59 Difference BetweenRefractive Indices — — 0.11 — B Layer Average Cross- 100 20 100 10000Sectional Width (μm) Accuracy of Cross- C, D A B C Sectional WidthAccuracy of Interval C, D A A A Accuracy of Cross- C A C A SectionalArea S1/S2 C C C A Number of Layers 3000 3000 600 13 Shape of Cross-Circle Rectangle Rectangle Semicircle Section Covered/Uncovered CoveredCovered Covered Covered Film Width (mm) 600 600 600 400 Film (μm) 500450 1000 1500 Thickness Transparency (%) 2 0.5 — 5 Ununiformity AverageLoss (dB) — — 0.5 — Loss (dB) — — 0.02 — Ununiformity Winding — 2 2 2 1Hardness Variation Example Example Comparative 17 18 Example 7 Resin AResin PET PET PP Additive PMP PMP — Refractive Index 1.59 1.59 1.48Resin B Resin PET PCT/I PC Additive Ti PMP — Refractive Index 1.59 1.561.59 Difference Between Refractive Indices — 0.03 0.11 B Layer AverageCross- 10000 200 — Sectional Width (μm) Accuracy of Cross- C A CSectional Width Accuracy of Interval A A C Accuracy of Cross- A A CSectional Area S1/S2 A A C Number of Layers 13 1200 — Shape of Cross-Semicircle Semicircle — Section Covered/Uncovered Covered CoveredUncovered Film Width (mm) 400 400 600 Film (μm) 1500 250 1000 ThicknessTransparency (%) 2 2 — Ununiformity Average Loss (dB) — — — Loss (dB) —— Non- Ununiformity Measurable Winding — 1 1 10 Hardness Variation

The present invention relates to a laminated film and a film rollthereof. A laminated film of the present invention is suitable for alight guide, a light collecting film, a light diffusion film, a viewingangle control film and an optical waveguide film. A laminated film ofthe present invention may be employed for an optical module, anilluminating device, a communication device, a display or the like.

The invention claimed is:
 1. A laminated film comprising a layer A madeof resin A and a layer B made of resin B that are alternately laminatedin the width direction, wherein the width of said film is 400 mm or moreand the number of layer Bs, each having a cross sectional width from 0.1μm to 10,000 μm, is 10 or more, wherein a distance P between adjacentlayer Bs is 0.90 times to 1.10 times as large as a distance Pc betweenadjacent layer Bs at the center in the width direction, adjacent layerBs exist continuously in a width direction for 300 mm or more, and theshape of said layer B is asymmetric relative to the center axis of saidlayer B in the thickness direction in the film thickness direction—widthdirection cross-section, and S1 is not more than 0.8 times as large asS2, and wherein said S1 and said S2 are cross-sectional areas of saidlayer B halved by the center axis in the thickness direction and S1<S2,wherein said laminated film is used as a light diffusion film, a lightcollecting film, or a viewing angle control film.
 2. The laminated filmaccording to claim 1, wherein a cross-sectional area A of said layer Bsis 0.90 times to 1.10 times as large as a cross-sectional area Ac ofsaid layer B, said cross-sectional area Ac being located at the centerin the film width direction.
 3. The laminated film according to claim 1,wherein resin B is a thermoplastic resin and more than half of saidlayer Bs are covered with resin.
 4. The laminated film according toclaim 1, wherein one of said resins A and B is soluble to a solvent towhich the other is insoluble.
 5. The laminated film according to claim1, wherein the cross-sectional width of more than half of said layer Bsis in a range of an average cross sectional width of ±10 μm.
 6. A filmroll made of the laminated film according to claim
 1. 7. The film rollaccording to claim 6, wherein the winding hardness variation in thewidth direction is from 0.0001 to
 6. 8. A display using the filmaccording to claim 1.